06-Sep-2011: A long overdue update

Hello, all,

I hope that this post finds the folks that visit this blog are doing well.

It has been a very long time since I have posted anything here. Some has been due to a lack of time, but the main reason, especially in the past eight months or so is due to a rare disease that I have become afflicted with. Symptoms of the disease started subtly about eight months ago. It started with tingling in my feet and lower legs, and some loss of sensation and numbness. It slowly got worse and so I got ahold of my doctor and made an appointment to go in. Doc verified that there was definitely some loss of sensation, and referred me to a neurologist. Thus began a long, and sometimes painful process of diagnostics to try to figure out what was going on. I had neck and spinal MRI, brain MRI, nerve conduction tests, spinal taps (A.K.A Lumbar Puncture, very painful), tons of blood draws for tests, electromyography (they stick a needle into muscle and measure its electrical signals),and what seemed like constant blood draws for all kinds of varios tests.

The result of it all was finally a diagnosis in late July.  I have MADSAM.  MADSAM is an acronym for Multifocal Acquired Demyelinating Motor and Sensory Polyneuropathy.  What this mouthful describes is an autoimmune disease where the immune system attacks the fatty myelin insulation that surrounds and protects peripheral nerves.  This insulation isolates the nerve electrically and physically from other tissues, helping the nerve to transmit its signals cleanly and with minimal signal loss.  When the myelin is damaged, the nerve signals get somewhat mangled as they traverse the nerves, resulting in poor quality signals that don’t accurately convey what is either being sensed or controlled.  This results in vague sensation (numbness, constant tingling sensation, and false pain), as well as loss of accurate muscle control, as well as trembling, twitching in the muscles, weakness, muscle pain, and fatigue.  There isn’t any understood trigger or cause for MADSAM, nor is there any cure.

Symptomatically, MADSAM is similar to ALS (also known as Lou Gehrig’s Disease), but ALS destroys the Schwann cells the regenerate the myelin, while MADSAM does not.  So, if the immune system can be slowed down such that the damage to the myelin doesn’t happen as fast, the Schwann cells can rebuild the myelin, which can result in the nerves getting better.  The issue is slowing down the immune system so that the nerves can heal.  There are a number of treatments that can suppress the immune system, none of which are much fun.  The most common is the use of high dose steroids (in this case, Prednisone) that slows the immune system down, but with some not-so-fun side effects, which include irritability, higher stress levels, weight gain and body fat redistribution (belly and face), thinning of the skin, easy bruising, increased appetite, and if used for long periods of time, increased risk of heart disease and some forms of cancer.  The other treatments are more harsh or difficult, which is why Prednisone is used most frequently, as it has the least effect on the patient.  The others involve use of some cancer chemotherapy drugs that have a similar immunosuppressant effect, but are much more harsh.  Plasmapheresis, which involves filtering the blood to remove immune system cells, is extremely expensive, and takes about six hours a day hooked up to a filtering machine.  These other treatments would have a serious impact on my ability to continue to work, so, the Prednisone is it, though it has not been much fun.

It takes quite some time for the Prednisone to suppress the immune system to the point where the attack on the nerve myelin slows down enough that the Schwann cells can begin regenerating it faster than the immune cells damage it.  Then, the myelin regeneration process is also very slow.  My neurologist says that it can take two to three months before symptoms can start to diminish.  I’ve been on the Prednisone about a month now.  In the meantime my symptoms continue to increase.  My legs are now mostly numb from just below the knees all the way down to the tips of my toes.  My legs are weak, and while I can still walk, my gait is clumsy, and I can’t walk on uneven surfaces, and running is dangerous.  Stairs are very difficult.  I have had a number of nasty tumbles, but so far, no serious injury.  My hands and lower arms are also being affected, which has slowed down my typing speed and increased the error rate significantly, and also made it more difficult to do fine, precision work with my hands, which certainly has an impact on my ability to work on some of the intracacies of old calculators.

With all that said, I am determined not to let this situation get me down. Once the diagnosis was given, it was actually a bit of a relief, because along the way there were talks of cancer, ALS, MMN (which is a similar disease to MADSAM, but is significantly worse), and Multiple Sclerosis.  I’m thankful that of all of these really bad diseases that MADSAM is probably the least of the bunch in terms of impact on living (or life itself).   I have had some times where I have been down and frustrated by this situation, but I have come to accept it, and am adapting as best as I can, and my outlook continues to improve over time. Hopefully the treatment will eventually lead to some reduction in symptoms.  In some cases, the Prednisone treatment actually can cause a “reset” of the immune system, which can lead to long-term remission from the disease.  In other cases, it is only a temporary fix, and symptoms may return.  The Prednisone can only be taken at high dosages for limited periods of time, so if I do get some relief, and later the symptoms come back, the treatment can resume, but only after a period of time for my body to “rest” from the side effects of the Prednisone.   I am hoping for the best, and working hard to keep the negative thoughts out of my mind.

On the calculator front, quite a lot has gone on over the past year or so..a quick overview

On the new calculator front, New Acquisitions:

• Monroe 820A(non-working), thanks to a generous donor,  to go along with the Monroe 820 that the museum already has (also non-working).  I am hoping that between the two of them I can get one working. This is the only CRT-display-based machine that Monroe made, and it is quite uncommon.
• A Monroe EPIC 3000 (in very nice shape, and mostly working), and a Monroe EPIC 2000 with some mechanical and electronic problems.  In time I hope to get the EPIC 3000 completely working…it seems like the problem is just a bad connection in the cable that connects the keyboard/printer unit to the electronics package.
• A Sharp Compet 21(CS-21A).  This is an extremely rare machine that looks identical to the Sharp Compet 20, but with electronics changes that allow it to perform square root.  The machine calculates square roots to five digits behind the decimal. The machine has problems, but I am hopeful that they can be figured out and repaired.  It tries to run, but gets very confused when asked to perform operations.  The design of the machine is very similar to the Compet 20, with some boards identical between the two, but there are definitely changes to the PP board (Program Package) that contain the sequencing logic for the machine, and addition of three unique boards, one of which appears to be a diode ROM that perhaps provides sequencing logic for the square root function, along with a significantly different keyboard interface board that probably detects the “divide followed by +=” key sequence that triggers the square root operation.
• A Sharp Compet 32 that will shortly be on its way to the museum.
• An additional Sharp Compet 20 that is a bit earlier than the one currently in the museum, which will be arriving soon.

Because of all that has been going on, updates to the Old Calculator Museum website have slowed to a trickle.  I have a large backlog of exhibits to create, and quite a number to update.  I also have more materials to add to the advertising archive, and some technical information to add.   The biggest enemy I have right now is time.

My job is keeping me very busy (and still thankful to have it, though there are days when it is difficult because of the neurological condition and symptoms of the Prednisone treatment). The University started fall session classes last week, and things are really hopping with over 3500 students now making demands of the computing environment, which we did a huge amount of work on over the summer. Along with work, during the summer months, there are constant projects around the property that demand time, along with my wife’s dog agility competitions that consume time on weekends.

I must veer off-topic for a moment. We have a German Shepherd that is competing at the top national levels of competition in dog agility, and this year has been extremely successful.  Tory (our German Shepherd) and my wife, Patty, have earned entry into three National Championship competitions this fall and early next year, including the German Shepherd Dog Club of America Nationals, the AKC National, and the USDAA National.  We’ll be traveling to Kansas, Kentucy, and Nevada for these competitions, and hopefully, come home with some national championships.  German Shepherds are very uncommon to run at the national level in a sport dominated by Border Collies and Australian Shepherds.  It is a huge testimony to the athletic abilities and high level of intelligence that Tory has, and Patty’s dedication to excellence in training (both for herself, and Tory) over Tory’s 5 years of life.  You can see YouTube videos of Patty and Tory in action by checking out the channel “pattybffds”.  Just search for it on YouTube.

Once the fall and winter settle in, there will be more time to devote to my calculator passion, and I expect that there’ll be a more updates both to this blog, as well as to the museum website.

Lastly, before I close out, I am honored to be invited to a gathering of ex-Friden employees (known as Fridenites) in San Leandro, California (the original headquarters of Friden Calculating Machine Co.) on September 15th.  This luncheon gathering will have many luminaries from the heyday of Friden, including Robert Ragen (the chief designer of the Friden EC-130), Dick Ahrens (a senior engineer involved in the design of the EC-130), George Comstock (another senior engineer, who left Friden to form Diablo Systems, a company famous for the development of daisywheel printer technology), and many other former Friden employees.  This should be a fun and fascinating time.  I will try to write up a blog entry about the event soon after I return.

With all that said, I will call this entry complete.  There’s a lot more that I didn’t write about, but that captures the high points.   I’ll try to make brief update posts at least once a month from this time onward, both relating to my condition, as well as any interesting calculator tidbits that I come across.

Wishing you all health (the most important thing), happiness, safety and security!

29-May-10: Jobfulness Thoughts, and a Recent Donation

It has been a long time since I’ve posted here – seven months. My aologies for taking so long. Time for calculator pursuits has been very limited lately. That’s a good thing, in that it means that I’ve been busy with other things, namely, my work, which is a blessing after having been unemployed for a long time.

It is coming up on a year being re-employed, and while it has it’s ups and downs, just like any job, it is so good to have one, especially in these times. For that, I am very thankful. It does mean that I have much less time to spend on the calculators, which can be frustrating at times simply because I really enjoy working on and documenting these relics. Being unemployed was great from the standpoint of time, but always has the gotcha of a bad money supply. When working, money supply is less of an issue, but, there goes the time. It is what it is, and trying to balance things out is all one can do.
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A few weeks ago, I had the extreme fortune to go pick up a treasure trove of old calculator equipment from a friend whom I’ve known for quite a few years. I came to know Gary Laroff when I started working for a local company that was in the process of spinning out of Tektronix in the mid-1990′s. Gary worked in the Marketing department of this company. As I came to know Gary, I learned that he had worked for Tektronix for many years, and in the early ’70′s, had been part of Tek’s calculator division, working in Technical Marketing. Of course, I was always pestering Gary for information about his times in the Calculator Division, and Gary was always willing to take time to chat.

During the time at the spinoff compay, I learned that Gary had written the field sales documentation for the Tek Model 21 and 31 calculators, as well as a bunch of other materials that were used in the technical marketing of Tek’s calculators and peripherals. I also learned that he had a treasured cache of old calculators and materials that he’d acquired along his travels, stashed in his attic. At the time, he had no intention of finding a new home for this stuff…it was too much a part of his history. Needless to say, over the years, I would ask from time to time what he was going to do with the stuff, and he invariably replied that maybe someday, he’d make it available to the Old Calculator Museum.

Over the years after the spinoff had been acquired by another company, and then yet another, Gary and I no longer worked for the same place. Gary eventually retired and become deeply involved with his passion of woodworking. A core group of four of us (me included) from that original Tektronix spinoff company kept in touch, and occasionally get together for an always enjoyable lunch, as well as occasionally exchange EMail about myriad topics; ranging from John Deere tractors to air compressors; auto repairs to power tools, not to mention technology and politics.

A little while back, Gary sent out an EMail to our little group (clearly targeting me) saying that he had to have his house re-roofed, and that the calculator stuff in the attic would have to be moved for the roofing to be done. He said that it was time for the calculator stuff to go, indicating that unless someone could be found that would be interested in this old stuff, that it’d go off to the recycler. Clearly, I couldn’t allow that to happen. Attangements were made for me to go over to his place (not very far from the museum) and haul the stuff off. I took my small pickup truck, expecting I’d have more than enough room to haul what he might have. Little did I know that the pickup would he packed full (including passenger compartment) before I made the trip home.

When I arrived, I got straight to work. Gary had sorted through the stuff and had it pretty well organized in the attic, along with some boxes of materials that he’d gathered together. When he opened the door to the attic, I was faced with three Tektronix Model 31 calculators (one the likes of which I’d never seen before, more on that later), a very early production Tektronix 4661 plotter with interface for the Tek 31 calculator, a Hewlett Packard 9100B with 9120A electrosensitive printer attached, an HP 9101A extended memory unit, an HP 9102A buffer box (allowing more than one peripheral to be attached to the 9100-series calculator), and an HP 9125A plotter. Along with that, there were a number of boxes of great stuff, which included a bunch of manuals (including two copies of the very rare Tek 31/31 Service Manual along with a preliminary-release copy of the same manual), a whole slew of Tek 31 magtape cartridges, a bunch of NOS custom function keyboard overlays for the Tek 31, a Tek 31/53 instrumentation interface (allows Tek 31 to connect to specific Tektronix TM-500 measurement instrumentation) and connecting cables, some NOS rolls of thermal paper for the 21/31 calculators, and various other tidbits that piqued my curiosity.

Among the curiosities included were a manual for the Cintra/Tektronix 926 Programmer for the Cintra/Tek 909 and 911 calculators. Hmm. Also found was a cable for connecting the 926 to a 909/911 calculator. Curious indeed.    When Gary was asked about these items, he commented that he had more stuff that was packed elsewhere that he needed to sort through, and that he thought there was a 926 Programer, and maybe a Tek 909, as well as a Tektronix Model 21.  I’m hopeful that there’ll be a return trip to Gary’s sometime soon to pick up these items.

The HP 9100B works beautifully, even the lamps that light up the stack register legends to the right of the CRT work.  It is in nice cosmetic condition, with just some minor signs of wear.  The 9120A printer will require some work…the platen that pulls the paper through has turned to oily goo…a malady common for synthetic rubber parts from the ’60′s and ’70′s. Electronically, the printer seems to want to work, it just has no way to move the paper.  The 9102A buffer box appears to work just fine.  The 9101A memory expander (magnetic core-based memory) also works, but not 100% — there are some memory locations that report memory protection errors even when the memory protect feature is turned off.  That’ll take some digging to figure out.

Of the three Tek 31′s, two are functional, but have display problems (very common because of the Sperry gas-discharge display modules outgassing).  One of the machines is catatonic, probably a problem with the electronics as the power supply seems fine.  One machine’s thermal printer has a drive belt for the platen that has disintegrated, but I happened to have a spare from a scrap Tek 31 that I found many years ago. I’m going to have to find a reasonably-priced source for some of the Sperry SP-322 and SP-333 display modules to bring the machines with failed displays back to full functionality. These display modules are still made by Babcock today, but are profanely expensive.

One of the Tek 31′s is very unusual, and may well be a one-of-a-kind item.  Gary explained that back in the day, he had thought that the color scheme used on the Tektronix 21/31 calculators was too “instrumentation” looking.  He believed that a different color scheme that looked more “computer-like”, might improve the ability to sell the machine as a computing device.  Tektronix was an instrumentation company first and foremost, and in spite of the fact that the Tek 31 calculator was for all intents and purposes a small computer (with alphanumeric capability, lots of memory, extensive programmability, and a large compliment of peripherals using a common peripheral bus), Tektronix never really understood the difference between selling instrumentation and computing gear.  Gary was able to convince Hiro Moriyasu, the VP of Tek’s calculator division, to give his color-scheme idea a try.  A prototype was made, essentially with a different keyboard bezel color scheme and a repaint of the cabinetry from Tek blue to a creamy tan color.   Internally, the machine was identical to a production Tek 31. This prototype machine was one of the Tek 31′s that Gary donated.  It was found to be functional, but the display modules had some problems..not all of the digits worked.  By scrounging between the other two machines Gary donated, I was able to find enough display modules that worked to get this machine 100% functional.  I intend to take some photos of it soon and update the exhibit on the Tek 31 to include it.  This color scheme makes the 31 look much more like a computing instrument than a piece of test equipment.  In my opinion, it makes the machine look less chunky, giving it a much more professional look.  According to Gary, only one of these machines was made as a proof-of-concept, but it never went into production. The serial number on the unit is “BB09″, which makes me wonder what machines made up BB01 through BB08?  Perhaps the “BB” prefix in serial numbers was designated for special builds for special purposes?  I wonder where BB01 through BB08 might be (or what fate they met), and what unique aspects they had?

The huge Tek 21/31 Service Manual is amazing. It provides insights to the design of the 21 and 31 calculators that could only be guessed at before. The exhibit on the Tek 31 has been updated recently to reflect some of the additional knowledge gained relating to the 15 chip microcoded LSI calculator chipset (manufactured by AMI as custom devices for Tektronix) used in these machines. I’ve got a lot more reading to do to mine for more details. I hope to be able to unbind one of these (they are spiral bound) and scan it, although the schematics will be difficult, as they are large fold-out sheets that will require either a larger scanner than I have, or stitching together multiple scans, which is very tedious. The manual also gives a lot of insight on the very elusive Model 21 calculator. It uses the same calculating board as the 31, with a much less-capable Programmer board. I had speculated that the 21 might be a 31 with a less capable programming unit, and that’s exactly the case. Now I just hope that Gary can find the Tek 21 that may be packed away somewhere in his home.

The two plotters (HP 9125A and Tektronix 4661) are very interesting devices. The HP unit uses servomotors rather than steppers. It’s basically an analog device with digital interface. The 4661 uses more conventional stepper motors for positioning the pen. Speaking of the pen, that’s going to be the most difficult part of getting these devices going. Does anyone out there have a clue where I might be able to find pens for these plotters? Originally, these plotters had small felt-tipped pens that snapped into the plotter’s positioner. Back in the ’70′s, it was probably not much of a problem to find pens for these plotters. Now
it is another story. The Tek 4661 came with some pens, but they are all dried out. They’re useful as models for what a pen’s form-factor should be, but that’s about it. I have no clue what the pens for the HP plotter should be. I’ve done some initial searching online for plotter pens, but can’t find anything for plotters this old. If you have suggestions, please leave a comment on this blog. I have not yet tried connecting the plotters up to their respective calculators as yet, but will be doing so soon. Hopefully they are still in operating condition.

This large donation of equipment is greatly appreciated. I wish to express my sincere thanks to Gary for his generous donation of all of this wonderful material.  As time permits, I’ll go through more of these treasures, and document what I can by updating exhibits and putting interesting tidbits of information here in the blog.

I hope to update the blog a little more frequently than once every seven months. Time will tell.

29-Oct-09: TI & Calculator Hackers

While it’s not vintage calculators at play here, I came across the following article today that is definitely interesting. There is relatively small but dedicated group of folks that have a keen interest in hacking calculators. The calculator make of choice for hacking is the TI 84+, a very capable calculator made by Texas Instruments. The article talks about a calculator hacker that figured out the keys to the encryption scheme that protects the TI 84+’s firmware from modification. Once these keys were hacked, it is possible to make changes, or even completely replace the firmware that forms the operating kernel for the calculator. Quite an amazing accomplishment.

However, Texas Instruments is not taking this at all well. The company’s legal department has sent DMCA (Digital Millennium Copyright Act) cease-and-desist letters to a number of folks who posted details and mods online for the TI 84+. In response, the Electronic Freedom Foundation (EFF) is backing the calculator hackers, stating that there is no harm in their activities since TI makes the code for the calculator available for download.

The article can be seen at: IEEE’s Spectrum Online Magazine.

Hacking calculators is not new. Back in the old days, a lot of modifications were made to calculators to augment or improve their function. In the days of mechanical adding machines, contraptions were built that used solenoids to activate keys on the keyboard to automate data entry and problem solving, with the printing action of these machines recording the results. Sometimes such modifications were used to make inexpensive numeric printers. Benson-Lehner made modifications to a Friden rotary electromechanical calculator to interface it to an electric typewriter that allowed the calculator to serve as a math unit for a system, called the Computyper, that would perform functions such as invoicing. Once electronics came on the scene, necessity being the mother of invention, all kinds of hacks were developed to allow the machines to be programmed or automated in various ways. Some calculator manufacturers would make machines that had chipsets that had more capability than the function keys on the keyboard allowed. This was done to provide a line of calculators with different functions depending on how many keys were available on the keyboard, and how the keys were wired. By rewiring keys, or adding additional keys, folks could access these additional functions. Folks also used scientific calculator chips as peripherals on early home computers to act as math co-processors.

With today’s calculators essentially being computers with LCD displays, USB and serial connectivity, flash memory for firmware storage, and lots of keys on the keyboard, it seems only natural that folks would want to customize their machines to their liking. While the author won’t condemn TI for their action, nor condone the activities of the “hackers”, it just seems to me that this making a big deal out of something that is a natural tendency of bright folks to do. Let’s hope that this all settles on its own and doesn’t result in a big waste of time and money for all parties involved.

11-Oct-09: Catching up

Greetings to all.

It has been a while since I’ve post anything here as a lot of things have happened since the last posting. The biggest news is that, after a long period of unemployment (almost two years), I have finally found a new job. With the economic conditions so poor, it was a very scary time to be unemployed. After a very long time of submitting applications, one finally came through with a request to interview. Thankfully, I did well enough to get offered the job, which I happily accepted. The job is working for a local university as their Technical Services Manager. The position involves leading a team of Information Technology professionals who are charged with growing, maintaining and supporting the university’s information technology infrastructure; including networks, computing resources, and telecommunications. I have been on the job now for a little over three months and am starting to get my feet under me. It is quite an experience working in an educational institution, as it is very different than the high-tech commercial environments that I’ve worked in for so many years. Surprisingly, at least to me, it is quite a technology challenge, because the student body and faculty always have very interesting things that they wish to do with the computing environment that can stretch the bounds of maintaining a secure and safe computing environment. I have a good group of people that I work with and am very glad to be back among the employed. The only downside is that it leaves much less time to work on the calculators, maintain the Old Calculator Museum website, and write in this blog. But rest assured, I’ll somehow find the time to keep things moving along.

On the calculator side of things, in early July the museum received a calculator that it has has been seeking for a very long time. A Wang 500-Series (Model 500-2TP) was recently acquired by the museum. It was made possible through the kindness of Mr. Tim Ogsbury, and also through the generosity of Mr. Arnold Allen. Tim had the machine in his posession for a very long time. It was owned by his father who used it in his business for many years. After his father passed away, Tim kept the machine stored away. In the course of doing research on the Internet, Tim found the Old Calcualtor Web Museum, and ended up writing an EMail asking if the museum might be interested in acquiring the calculator. At the time, I was unemployed, and had virtually no financial resources to make a fair offer on the calculator, much less pay the costs for packing and shipping it to the museum. I sadly replied indicating that it just couldn’t work out at this time. Tim wrote back and said that he was willing to be patient. After some months, Tim wrote to me saying that he was going to have to move, and that it’d be best if the calculator could be shipped out before the move. Still unemployed, I was in a real quandary…there was just no money to be had. As it happened, I had been engaged in on-going dialog with Mr. Arnold Allen, a frequent donor to the museum who has sent a great deal of wonderful calculator and computer materials over the past nine months. I had mentioned in passing that an opportunity had come up to acquire a Wang 500, and Arnold immediately indicated an interest to help. A few days later, a check appeared in the mail with a donation that would cover the necessary expenses for the museum to acquire Tim’s calculator. Shortly thereafter, the machine was on its way to the museum. Suffice it to say that I can’t begin to express my gratitude to both of these wonderful gentlemen for making it possible for the museum to acquire the last machine in the “triple-crown” of the Wang 500/600/700-Series machines.

The Wang 500-series calculators consisted of two models, the 500, and 520, with the main different between the two models being the amount of memory available. The 500-Series calculators grew out of a perception within Wang Labs that it’s flagship machines, the 700-Series calculator (see the exhibit on the Wang 720C for more information on the 700-Series calculators), were too complex and expensive for some buyers. The 700-Series machines had extensive I/O interfacing capabilities that in many cases weren’t really needed for mathematics, scientific, and engineering calculations. The 500-Series was conceived as a high-end programmable calculator with only very basic I/O capabilities, much more suitable for general calculating requirements. Along with the removal of the advanced I/O capabilities, advances in integrated circuit technology, combined with the use of Metal Oxide Semiconductor (MOS) Random Access Memory (RAM) to replace the expensive magnetic core memory of the 700-series, allowed the 500-series to be less complex, and thus, less expensive. Along with these changes, the 500-Series also moved away from the rather unique 2-level stack architecture (X and Y register) of the 700-Series, going back to an architecture similar to that of Wang’s earlier, but market-making 300-Series calculators (see the Wang 360E exhibit for more information), which provided two complete arithmetic units called the “Left” and “Right” adders. This architecture, while unusual, was quite powerful. The architecture was extended by allowing memory registers to behave the same as these two built in arithmetic units, providing full add/subtract/multiple/divide capabilities for all memory registers. While somewhat different in terms of electronic implementation and operational architecture, the 500-Series calculators stuck with the basic microcoded architecture of it’s big brother. The microcode word in the 500 was shortened to 42 bits versus the 43 bits of the 700-Series, but the ROM was essentially identical to that used in the 700-Series, simplified slightly by use of IC-based sense amplifiers and latches.

The machine arrived during the day while I was at work. When I got home that evening, it had been signed for by my wife, and was waiting for me over in the museum building. I went over to check it out. The box looked to be in pretty good shape…no big holes or caved in areas, which was a good sign. The machine was packed quite well, double boxed, with lots of padding materials to isolate the machine from shock. The calculator looked to have made the trip from New York with no obvious visual damage. The machine was a little grubby, partly from years of use, and partly from simply being stored away for so long. It came with the original dust cover, the original Operating and Programming manual, a soft-bound publication containing listings of programs from Wang’s 500-Series program library, a couple of original pads of programming forms, and quite a few cassette tapes used for storing programs and data.

The 500-Series calculators made some changes over the 700-series, by making the cassette tape drive an optional component, as well as adding another optional device, a built-in 21-column printer. The machine obtained by the museum has both of these options. The printer was added as an option to the 500-Series because of the primary complaint of 700-Series customers…the lack of printed output. To get printed output on a 700-Series calculators, one had a to purchase a rather expensive modified IBM Selectric Typewriter that could be connected to the calculator through its I/O capabilities. This added even more cost to the expensive base price of a 700-Series calculator. The Seiko-made drum impact printer offered on the 500-Series calculators was a much less expensive alternative, and yet still provided the capability of providing formatted and annotated output under program control, as well as hard-copy of entry and results when using the calculator manually.

A curiousity of the 500-series is the decision by Wang to make the cassette tape drive an option. With the 500-Series machine using solid-state memory for its memory and program storage, programs and data stored in the machine are lost if the machine is powered off. With the 700-Series’ magnetic core memory, the state of the memory is maintained when power is removed. This seemingly makes the cassette tape even more necessary on the 500-Series machines, as the only other way to reload a program into memory once the machine has been powered off would be to key it back in by hand from the keyboard…a rather slow and tedious process. The cassette was mandatory on the 700-Series, yet made an option on the 500-Series. The only reason that I can think of for this is that Wang wanted to allow a 500-series to have a market-making price point for a stripped down machine, providing great fodder for marketing bragging rights, while not really providing a very usable machine in practical terms.

After a visual inspection of the outside of the machine, it was time to take the cabinet off, and see how things faired inside. Again, there was no sign of any obvious damage. All of the circuit boards were well-seated in their sockets, the Nixie tubes were all intact, and there was nothing loose rattling around inside the machine. The keyboard looked to be in good shape. The cassette drive, however, had some problems, which are not at all uncommon on these machines. The main drive belt that links the motor to the tape transport had disintegrated. These belts are made for a rubber-based compound, kind of like a rubber band with a cylindrical profile. Over time, ozone and other components of the atmosphere attack some of the chemicals that make up the belt, causing it to turn gooey. Over time, the belt literally dissolves, leaving nothing but oily goo in its place. This isn’t the first time that I’ve encountered this on Wang 500/600/700-Series machines (the tape drive assembly is the same across all of the machines in the line), so it’s no big deal — finding an appropriate replacement drive belt is not a big problem.

The next step was to pull out all of the circuit boards and inspect them for any signs of damage. This involves very carefully looking at the boards through a magnifier to check for overheated components, obvious broken components, corrosion, and other maladies that can affect circuit boards when stored for long periods of time. All of the boards looked good with the exception being corrosion on the tin-plated edge connector fingers — a very common occurrence on all of Wang’s calculators. The 500-Series continued Wang Labs’ practice of stamping each circuit board with an inspection date, with the boards in this machine having dates ranging from late 1971 through early 1972. After the boards were removed and their edge connector fingers cleaned, it was time to pull the keyboard and check it out. As the keyboard was removed, a piece of what looked like plastic fell out from inside the keyboard assembly. Wang’s keyboards for were known for their microswitch-based design which made the keyboards have a very unique feel…very short key travel with a positive ‘click’ as the key was actuated. As it turned out, the piece of plastic was part of one of the many microswitches that make up the keyboard. This meant that the keyboard had to be completely disassembled to repair the broken switch. This wasn’t a big problem, because the keyboard was pretty grimy and needed cleaning anyway. It’s much easier to clean the parts of the keyboard when it’s all disassembled. Once the keyboard was apart, the offending microswitch was pretty obvious…it was missing part of its case. The switch still worked properly, but in the interest of long-term reliability, I decided to replace it. The bad switch was carefully desoldered, and a replacement switch (from a spare 700-Series keyboard) was put in its place. The keyboard circuit board was inspected for any other problems, and everything else looked good. The rest of the keyboard assembly was thoroughly washed and cleaned, and once everything had dried, the keyboard was re-assembled, and once finished, looked almost new.

While waiting for the keyboard parts to dry, the electronics chassis was lifted out of the cabinet base. This was done because the microcode ROM is located underneath the chassis. This is a somewhat delicate operation, as there are two connectors that go from the backplane of the machine to the ROM, and the cables are rather short. The chassis is pretty heavy, and it must be carefully held up and away from the ROM while the connectors are removed, then the chassis can be moved away. Dropping the chassis on the ROM would likely cause irreparable damage to the ROM, meaning great care must be taken. It really should be a two-person job, but after lots of practice on 700-series machines, I’ve gotten good at performing this operation by myself. As an aside, it should be noted that the 500, 600, and 700-Series machines all share the same basic mechanical design. The cabinet base is the same for all of the machines, the main chassis is very similar, and the upper cabinet is also similar between all of the machines.

The ROM is one of the most critical, and also most prone to failure, parts of the 500/600/700-Series calculator. One tiny broken wire, or any type of electrical fault (a bad transistor or diode) will either render the machine completely non-functional, or cause malfunctions that effectively render the machine useless. The ROM is a very delicately made contraption consisting of literally thousands of tiny enamel-insulated copper wires (just about the diameter of a human hair) that are hand-threaded through horseshoe-shaped ferrite elements to encode the bits that make up the microcode that controls the operation of the calculator. The ROM has a plastic cover over it that protects the delicate wiring. This cover is taped to the metal frame of the ROM circuit board with simple transparent tape. The tape was carefully removed, and the cover taken off so that the ROM wiring could be inspected. It’s impossible to trace each and every wire…there are simply too many of them, and with all of them looking the same, it’d be way too tedious. The ROM was inspected with a magnifying glass to see if there were any obvious problems, and none were seen. The rest of the board was inspected, looking at the electronics to see if there were any obvious component failures or other issues. The ROM looked good. The cover was replaced, and the ROM set safely aside.

The chassis was then inspected. The 500-series machines implemented a change from the 700-Series calculators. The 700-Series machines used a hand-wired backplane, with long tailed edge connector sockets to which special clips attach. These clips allowed wires to be mechanically and electrically attached to the edge connector socket terminals. Wiring the backplane on a 700-Series machine was another example of a tedious manual process that was performed by very patient assembly line workers. The 500-Series machines dramatically simplified the wiring job by replacing the vast majority of the backplane wiring with an etched circuit board providing the connections between the edge connector sockets. The only point-to-point wiring that was required was that of connecting the rest of the machine (ROM, keyboard, cassette drive, printer, and power supply) to the backplane. The power supply, though of a very similar design to that of the 700-Series, was also simplified by use of a circuit board versus point-to-point wiring.

The backplane was inspected, along with the power supply components, and all looked good — no broken wires or signs of overheated or stressed components. With everything taken apart, it was now possible to power up the machine to test the power supply. The power cord was plugged into a variac, and a number of digital voltmeters were connected to various spots in the machine where the various power supply voltages were expected to be present. The power was turned on, and the variac slowly ramped up to 100% line voltage. As the supply was ramped up, the DVM’s started registering. By the time the power was at 100%, all of the voltmeters were showing voltages that appeared to be in-line with expectations. The oscilloscope was fired up and connected to various places to check for power supply ripple. Excessive ripple (basically, a low-level alternating current riding on top of a direct current voltage) can cause digital logic to malfunction (at best), and at worst can actually cause component damage and failure. Ripple is caused by the fact that transformers work on alternating current…a current that switches direction once every 1/60th of a second. Diodes are used to split off the positive and negative transitions of the alternating current in a process called rectification that allows a direct current to be made from alternating current. Capacitors are then used to smooth the switching transients caused by the diodes to allow a clean, stable direct current (DC) voltage to be formed from the alternating current (AC) output of the transformer. The capacitors that perform this function are called filter capacitors, and are typically high capacitance electrolytic capacitors. These devices, if not used for long periods of time, can have electrochemical reactions that occur inside them that reduce their effectiveness, which can result in the diode switching transients leaking into the DC signal, which, as mentioned earlier, can cause havoc with the digital logic. Fortunately, all of the various DC voltages used in the machine had ripple voltages that were well within acceptable ranges. This meant that the power supply was in good shape.

With the power supply checked out, it was time to put everything back together again, and see if the machine would run. The machine was carefully re-assembled, with every connector and circuit board triple-checked to assure that it was installed in the right location and orientation.

At last, the moment of truth. The Variac was again used to power up the machine. As the voltage neared 100%, only one Nixie tube was glowing, and it had multiple digits on at the same time, creating a “fuzzy orange” appearance rather than that of any distinct digit. This behavior continued once the Variac was at 100%. I wasn’t too worried at this point because when powered up slowly with the Variac, the calculator’s power-on initialization circuitry can’t work properly. So, the [PRIME] key was pressed. Wang, for whatever reason, started calling their “reset” button PRIME on their earliest LOCI calculators. This persisted through the 500/600/700-Series calculators. When the [PRIME] key was pressed, while the key was down, the display was blank (which is normal behavior). When released, sadly, the “fuzzy orange” tube was again lit, and there was no response at all to the keyboard. This is a symptom that I’ve observed on many 700-series calculators indicating that there’s definitely an electronics problem, most likely either in the ROM, or with the random access memory system. It will take some detailed digging into the machine to figure out what is going on. All I can hope is that the ROM doesn’t have broken wires, as repairing such a failure is virtually impossible.

Because of the new job, I haven’t had much time to spend digging into the machine further, though with fall arriving, the pace of various projects around the house that consume time on the weekends is beginning to slow down, and I should have more time to work on the long list of projects that have accumulated. I have quite a backlog of exhibits to create, repair work on the Wang 370 programmer to complete, and of course, diagnostics on the Wang 500, which I am hopeful I can get running again.

Other things brewing — I have received an original drive belt for the Wanderer Conti calculator from my friends at the Heinz Nixdorf Museum in Germany. They have a number of Wanderer Conti calculators, and were kind enough to send a drive belt on loan so I can look into trying to find something similar from a supplier, or at worst, have an equivalent manufactured. The museum was donated a Monroe 1655 programmable calculator in fine condition, which I’m working on getting documented in an exhibit for the museum. The Monroe 1655 is an example of the first-generation of Computer Design Corporation (a.k.a. Compucorp)-designed advanced desktop Nixie-display calculators. The most interesting thing about this particular machine is that it is the earliest example found of this first-generation Compucorp architecture. There are some historical tidbits that I ran into while digging into this machine as part of preparing the exhibit, which should be good reading for visitors once I finish it.

I am looking forward to the opportunity for a return visit to the museum by Bob Norman (see the May 21st Posting – Distinguished Visitor) during the rapidly approaching holiday season. I hope to soon publish an essay that has been a work-in-progress for a long time relating to the development of the amazing Victor 3900 calculator, just one of the many projects that Bob worked on during his illustrious career. Bob’s insights have been profoundly valuable in documenting the story behind this historic calculator.

Until the next time, I wish everyone health, safety, peace and happiness.

06-Jun-09: Fantastic Donation

Last week, the Old Calculator Museum received a very special calculator as an addition to the museum’s inventory. The machine received was a 1965-vintage Wanderer Conti printing electronic calculator.

Back in early November of 2008, the museum was contacted by Mr. Hans Boeck, indicating that he was in possession of a Wanderer Conti electronic calculator that was demo machine used by Mr. Boeck when he was involved in sales of electronic calculators in the international market. Mr. Boeck had indicated that he would be interested in donating this machine to the Old Calculator Museum. Due to a number of complications, it took quite some time for the machine to finally make its way to the museum. It arrived completely intact, a testimony to the incredible packing job done by Mr. Boeck. The Old Calculator Museum owes a supreme debt of gratitude to Mr. Boeck for making this wonderful artifact available to the museum. The Conti is a rather rare machine, and while it was sold in the US by Victor Comptometer (under OEM agreement with Wanderer-Werke) as the Victor 1500-Series, there just are not very many of these machines left around today. The museum has been looking for an example of a Conti (or the Victor or Sumlock Comptometer-badged versions of the machine) for many years. Had it not been for Mr. Boeck’s kindness and generosity, the search may have gone on for a very long time.

The Wanderer Conti was the first electronic printing calculator to print on “adding machine-style” paper tape. The Mathatronics Mathatron is historically recognized as the first printing electronic calculator, but it printed on a special 5/8ths-inch wide “ticker-tape” style paper tape. While the Mathatron had the distinction of being the first marketed printing electronic calculator, the ticker-tape style printout was somewhat unwieldy for storage and reading, while the adding machine tape printout of the Conti was something that was much more familiar to accountants and bookkeepers. The Mathatron was more targeted at scientific and engineering calculations, while the Conti was more targeted toward business use.

Wanderer-Werke AG, a company founded in 1885 in Koln, Germany, started out manufacturing bicycles. The business thrived, and into the early 1900′s, the company had expanded into making typewriters, milling machines, and by 1910, had started making automobiles and motorcycles. The company became known in Europe as a premier manufacturer of mechanical products of superb engineering. In 1927, the company began manufacturing adding machines, further expanding their business base, and making a name for itself in the European business machine marketplace. During World War II, Wanderer-Werke was a principal manufacturer involved in the German war effort. After the war ended, the company went back to its core businesses. Wanderer-Werke AG still exists to this day, serving primarily as a financial holding company for a number of businesses, as well as licensing the Wanderer brand name for use by outside companies.

With the advent of the first marketed desktop electronic calculator, the Sumlock Comptometer/Bell Punch ANITA in late 1961, many makers of mechanical adding machines and calculators began to realize that their future in the business machine marketplace may be radically affected by the advent of electronic means of calculation. It so happened that one of Wanderer-Werke’s major customers was another German company, Labor Für Impulsetechnik, also known as LFI. Founded in 1952 by Heinz Nixdorf, a brilliant electrical engineer and businessman, LFI developed complex electrical and electronic control systems for industry. Mr. Nixdorf had a keen interest in computers, and moved his business into developing electronic computing devices, developing early business-oriented small computers and accounting machines. Sometime in 1962, and arrangement was made for LFI to design the electronics for Wanderer-Werke to use in making their own electronic calculator.

LFI had a world-class electronics design operation, and had become masters in the art of designing logic circuitry based on transistors. Up until 1958, Mr. Nixdorf was the chief electronics engineer for the company, but after that, he had to start hiring engineers to help with the design process, as there was simply more work than he could handle by himself. LFI designed all of the transistorized electronics for the machine to specifications jointly developed by Wanderer-Werke and LFI. In late 1964, the first Conti (which derived its name from Wanderer’s line of “Continental” typewriters), was introduced in Europe, and was quite successful due to its convenient printing operation, high speed, and memory capability. In 1965, Victor Comptometer signed up as an OEM distributor of the machines in the US (marketing the machines as the Victor 1500-series calculators), and later (1967) Sumlock Comptometer in the UK also distributed the machines to provide a printing calculator to their existing line of Nixie-tube display calculators.

The design that was developed was truly a work of digital design art for the time. The calculator’s architecture was a bleeding-edge example of computing machine design, using a microcoded architecture centered around a wire-rope ferrite core ROM for controlling the operation of the machine (14x16x80, for a total of 17920 bits of ROM), magnetic core memory (16x14x4, totaling 896 bits), and completely transistorized control logic and arithmetic unit. At the time of its introduction, there was no other machine on the market that could match the Conti as far as the advanced computer-like architecture used in its design.

The resulting machine was built to the extremely high standards of German manufacturing processes. The design is very modular, with the electro-mechanical keyboard and printer assemblies, and power supply module stacked neatly atop the electronics. The electronics are in the form of three large circuit boards, arranged in plastic frames and “bound” at the long edge such that the boards form a “book”. The boards are interconnected by hand-wired connections along the spine of the book, along with four very high quality edge connector sockets that make up the backplane connections as well as the connections between the keyboard/printer, power supply, and electronics. The power supply takes up the right-hand side of the chassis, the printer situated in the center, and the keyboard mechanism at the front of the machine. The electronic design is based on Silicon transistors, making the Conti the earliest electronic calculator based on this transistor technology. Other electronic calculators of the time were based on earlier Germanium-based transistor technology, that used more power, operated at slower speed, and tended to be less-reliable than Silicon-based transistors. The speed of the Silicon transistors, combined with the efficient microcoded architecture of the machine made the Conti a very fast calculator. Additions and subtraction took just over 1 millisecond (1/1000th of a second), and multiplication and division took between 60 and 70 milliseconds. By comparison, the Friden 130 was roughly 20 times slower on average. Of course, the Friden machine displayed its answers on a CRT display, giving virtually instantaneous results once the calculation was completed, while the Conti had to take the time (roughly 300 milliseconds) to print its results, but for the extra time spent, the Conti gave a permanent record of its calculations, something the Friden and most all other calculators on the market at the time could not boast.

The mechanicals of the Conti live up to Wanderer-Werke’s mechanical engineering excellence. The design of the printing mechanism is relatively compact and quite straightforward, using individual print wheels for each column. The print wheels turn to match up with corresponding digit or character needed at that each position, at which time a small solenoid is fired by the electronics to lock each wheel in place. Once all print wheels are in the correct position, the mechanism drives the print wheels up against the ribbon to transfer the line of print to the paper in one shot.

The keyboard assembly is a very complex mechanical assortment of code bars that serve to encode the keys, switch contacts to turn the mechanical code into electrical impulses, and interlocks to prevent multiple keys from being depressed at once.

While there are different versions of the Conti, they all share some common features. The machines have a capacity of 14 digits. Internally, 16 digits are used (the machine uses a 4-bit “word” to encode each digit), with one digit representing the sign of the number, fourteen digits making the number, and a final digit used as a “check” digit by the electronics as an error-detecting means. All of the machines have at least three memory registers, with some models gaining an additional seven memory registers for a total of ten memories. All of the models provide the four standard math functions, with some models able to calculate square roots with one-touch ease. Fixed decimal point location is set by a thumbwheel switch. On some models, two thumbwheel switches allow setting of the decimal point location and the digit at which round-off/truncation should occur. The keyboard provides a key for forcing the current number to be rounded off or truncated based on the setting of the round-off switch. Negative numbers are printed in red, using a two color ribbon. The printer has 21 columns, and can print around 3 lines per second. Later models in the Conti line, based on the same basic design, allowed the connection of external peripheral devices such as a paper tape readers (for automatic input), paper tape punches (for recording output of the calculator), other forms of hard copy (slave printers and typewriters), and even magnetic tape drives that would record the calculator’s output to allow it to be fed to computers.

The machine received by the museum has three memory registers, one-key square root, and provides separate thumbwheel controls for selecting the decimal point position and the round-off digit position. It does not have provisions for connection of peripheral devices.

In a competitive analysis document published by Friden Calculating Machine Co. in 1965, Friden commented that there was a lack of information about the machine that kept them from performing a detailed analysis. To this day, this statement is still true, there is very little information out there about these fantastic machines. The authors of the Friden document did comment that in the demo that they saw, the keyboard seemed to be a weak point for the machine, with the comment made that operation of the keyboard seemed less than satisfactory. They also commented that the machine seemed complicated to use, with a large number of control keys.

While the Conti was not a programmable machine, the fact that it was controlled by a microcoded calculating engine meant that it was possible for custom operating firmware to be created for the machine. While not substantiated as ever having been done, the Friden document noted above does mention that customization of the machine can be done, but not by the user. Such customization would likely be done by modifying the content of the microcode ROM to implement customized functions for particular applications.

The machine does have a few minor issues known at this time that need to be worked on. First, there is a cogged belt that connects the main drive motor to the printing assembly. Somewhere along the line, this belt deteriorated, as is common with many rubber-based materials that are exposed to many years of atmospheric contaminants. Unfortunately, this belt is of a size and cog pitch that does not seem to be made anymore, so some effort and expense will have to be expended to have a custom-manufactured replacement made. Also, the main clutch that actuates the printing mechanism doesn’t completely release at the end of a print cycle (as found by manually cycling the machine through a print cycle), meaning that some adjustment of the mechanism is required. Also, the memory register selection keys (three of them) are all locked in the pressed position, which will likely require some mechanical adjustment to remedy. Along with these mechanically-related issues, the machine will need a thorough electronic checkout to assure that all is well with the power supply before even thinking about powering the machine up.

I have written to the Curator of Business Machines at the Heinz Nixdorf Museum in Paderborn, Germany, in hopes that they may have information about the Wanderer Conti calculators. Hopefully this query will result in some materials which can be used to help better document this machine in an upcoming exhibit on the Old Calculator Museum’s website.

21-May-09: Distinguished Visitor

Sorry it has been a while since I have posted here, I’ve been quite busy with many different projects around the property now that the weather is starting to get better.

On Monday, May 18th, the Old Calculator Museum was most honored to be paid a visit by none other than Robert Norman, one of the founders of General Microelectronics (GM-e) – the company that made the first production Metal Oxide Semiconductor (MOS) integrated circuits, along with creating the historic Victor 3900 electronic calculator. The Victor 3900 was the first calculator in the world to use “large scale” MOS integrated circuits.

Bob had occasion to visit the West Coast (he lives in Massachusetts) because he was invited to attend the Computer History Museum 50th Anniversary celebration of the invention of the Integrated Circuit. Bob is considered a luminary in the semiconductor world due to his many contributions as both an engineer and businessman, heavily involved in the development and advancement of Integrated Circuit technology.

Bob has family in the Portland, Oregon vicinity, and after his visit to CHM to attend the anniversary celebration, he came to Portland to visit family. I received an EMail from Bob’s Granddaughter last week asking if there would be a good time to get together. After some dialog, it was decided that Monday afternoon we would get together for lunch in Oregon City, and then after lunch, we would go to the museum so Bob could see it, then have some time to talk about Bob’s experiences back in the “Wonder Years” of IC technology.

We arranged to meet up at a restaurant in Oregon City at 2 o’clock Monday afternoon. I met Bob, his Granddaughter, and his Great-Granddaughter at the restaurant. We had a wonderful lunch, with Bob sharing all kinds of wonderful stories, mostly about his days at General Micro-electronics, specifically relating to the development of the Victor 3900 calculator.

After lunch, they followed me from the restaurant out into the country where my home and the Old Calculator Museum are located.

Once we arrived, we first went to the museum building where Bob and his family members could see the museum. Bob’s granddaughter and great-grandaughter took a lot of photos of the various machines, and of Bob looking over the museum’s collection. Bob was tickled to see the Victor 14-332 in the museum. The 14-322 was Victor’s later follow-on to the Victor 3900, using a similar logic design, though the logic devices used were small-scale bipolar DTL and a delay line, rather than the large-scale MOS used in the 3900.

Bob saw a number of Sharp calculators in the museum’s collection, and immediately related stories about his relationship with Tadashi Sasaki, the famous “Mr. Rocket” at Sharp, who was responsible for Sharp creating the second (the Victor 3900 was the first) Large-Scale MOS calculator, the Sharp QT-8D. It seems that Bob and Mr. Sasaki were close friends. Bob spent a lot of time in Japan, especially once he had left GM-e and started up his own company, Nortec Electronics. Mr. Sasaki would make it a point to fly the American flag at Sharp headquarters whenever Bob came to visit. It is hoped that someday in the future, Bob can share some more stories about his relationship with Mr. Sasaki.

After about an hour or so of wandering around the museum, with me telling stories about some of the interesting machines, we went to the house to sit down and let Bob talk about his days at GM-e and the development of the Victor 3900. Two hours flew by so fast that it was almost scary. I was totally engrossed in the amazing stories that Bob had to tell. Bob’s memories of these times are impressively clear, with he recollections flowing as if these events had occurred just days ago rather than 45 years ago.

A great many mysteries concerning the development of the Victor 3900 were cleared up by Bob’s recollections. The story of GM-e and Victor’s collaboration in the creation of the Victor 3900 is a wonderful story that needs to be told.

Alas, the time came when the visitors had to leave. Bob mentioned that he has plans on returning to the area during the Christmastime. I am hopeful that we’ll be able to get together again during the holidays.

As a result of all of the fantastic information that Bob has provided, both through EMail dialog, and our wonderful visit, I am working on an essay on the development of the Victor 3900, and some of the interesting outcomes that resulted from the amazing technology that GM-e developed to make the calculator a reality. Watch the Old Calculator Museum website for this essay, which will hopefully be published sometime in June, after Bob gets a chance to review it.

I wish to express my sincere thanks to Bob for coming to visit, to his grand-daughter for bringing Bob out to the sticks to visit, and for Bob’s great-grand-daughter for her patience while her great grandpa and I babbled on about technology.

16-Mar-09: One Step Foward… [More Wang 370]

In the last post concerning the Wang 370, the 371 punched card reader was checked out and appears to be generally healthy. In spite of this, the 370 still has problems with hanging when simple program-related functions are attempted. After looking through the logic, the first place to check is the master clock and timing chain.

The bottom cover of the 370 was taken off, providing access to the backplane connectors. This would be the best place to connect an oscilloscope to monitor signals on the backplane.

One Logiblock (#571 – System Control) contains the master clock oscillator and the three timing chain flip flops connected as a simple three bit binary counter. A scope probe was placed on the backplane pin containing the master clock signal. The 370 was disconnected from the 360E electronics package, and the 370 powered up. Immediately, the oscilloscope showed a reasonably clean, symmetrical square wave at a frequency of about 36KHz. It was clear that the master oscillator was running just fine. Next, the probe was moved to the output of the first stage of the timing chain. Interestingly, the output was static, with only tiny (a few millivolts) transients occurring occasionally. If the flip flop was working properly, this output should be a square wave running at half the frequency of the master clock. Clearly, it wasn’t. This in itself was a big clue. If the timing chain isn’t running, the logic states that sequence the 370’s logic can’t operate properly. This could well be the reason why the 370 hangs when trying to perform a simple single-step operation.

Just out of curiosity, the outputs of the two other timing chain flip flops were checked, and they too were static, which would make sense, as these flip flops are clocked by the action of the first flip flop.

The outputs of the timing chain flip flops are passed across the backplane to another Logibloc (#570 – System Timer) that contains, among other things, combinatorial logic that decodes the outputs of the timing chain flip flops into a series of timing signals that choreograph the operations of the 370’s functions. To see if perhaps there might be a fault on this board, the board was removed from the backplane, and the 370 powered back up. This time, each of the three timing chain flip flop outputs (T1, T2, and T3) were wiggling the way they should, with the first stage output at half the speed of the master clock, the second stage at one quarter the rate of the clock, and the last stage at 1/8th the master clock frequency.

It seems that something in the System Timer Logibloc was interfering with the output of the first stage of the timing chain. The combinatorial logic on the System Timer board consists of diode-resistor networks configured as AND gates, with transistor stages providing inversion and/or buffering of the gate outputs. There are a number of these logic networks that decode various states of the timing chain flip flops. All of the diodes in the gating networks were tested in-circuit using the diode check mode of the DVM, and they all appeared to be OK. Resistors were measured for proper resistance values, and all were within spec. So, attention was turned to the transistors. A shorted transistor could easily drag down the output(s) of the timing chain flip flops.

Testing transistors in-circuit can be a hit or miss proposition. It is much better to remove the transistors from the circuit, and test them individually. The difficulty with this is that the Wang Logiblocs were hand-assembled. At the time this 370 was manufactured (1969), automated component insertion equipment was very rare. Thus, components were manually inserted into the circuit boards, with the leads bent over on the wire side of the circuit boards to temporarily secure the parts on the board. Once all of the components were installed, the boards were flow-soldered. This makes component removal a little difficult, because with the component leads bent over, the solder needs to be removed, then the leads unbent carefully, and then any residual solder removed while the component is very carefully extracted from the circuit board. A high quality temperature controlled soldering iron, combined with a vacuum solder-removal system makes it possible to remote components, but even with these tools, component extraction is still tedious and time-consuming.

It was decided to remove the seven transistors involved in the timing chain decoding logic and test each of the transistors using a transistor tester.

All seven transistors (RCA-made 2N404 Germanium PNP transistors) were carefully removed from the circuit board, and each was tested. As it turned out, one transistor was found to be bad. It had a short between collector and base that applied -11V to the output of the diode gating network. This served to drag the output of the T1 timing chain flip flop down to near -11V. This was certainly the reason why the timing chain flip flops weren’t running properly. The defective transistor was replaced with a known-good one (the museum has a stock of spare parts for the Wang 300-Series calculators) and all of the transistors re-soldered back in place on the 571 board.

The 571 board was replaced in the backplane, and the scope set up to monitor both the master clock signal, along with the T1, T2, and T3 timing chain flip flop outputs. Power was applied, and low and behold, all three flip flops were flipping and flopping exactly as they should be. To double check, the outputs of each of the logic networks that decode the various states of the timing chain flip flops into timing phases that sequence the operations of the 370 were tested, and each output was as-expected, depending on the state of the three timing chain flip flops at any given point in time.

Now that the timing chain was running properly, it was time to see if programming operations would function properly without hanging the 370.

The 371 Card Reader was connected up to the 370, and the 370 plugged into a Wang 360E electronics package. When powered up, the display showed “+0.000000000” as expected. A program card had been prepared, punched with codes to perform keypresses of [1], [2], [3], followed by a STOP instruction. This program, if it ran, should result in “+123.0000000” being shown on the display.

The card was loaded into the reader, the [PRIME] key pressed to initialize the calculator and the 370, and then the [CONTINUE] key was pressed, which should start the program executing. Nothing happened. The display still read “+0.000000000”. Pressing the [DISP PROG] key showed that the program counter was at “00”, and the step at that location was as it should be. It appeared that the program did not run, as if it had, the program counter should have been something other than “00″. The [DISP PROG] key was released, and the display reverted back to “+0.000000000” as expected. Then the [STEP] key was pressed (with no apparent response by the machine), followed by again holding the [DISP PROG] key. The machine still said that the program counter was still at “00”. If the STEP function worked properly, I would have expected the program counter to have incremented to step “01″. It didn’t.

It appeared that some problems still exist. Just out of curiosity, the [PRIME] key was pressed, followed by the [7] key, just to make sure that the 370 was still talking to the electronics package. Nothing happened. A number of different key-presses were attempted, and none of them had any effect – the display just kept reading “+0.000000000″. Pressing the [PRIME] key resulted only in a slight dimming of the Nixie tubes – not a good sign. I powered everything down and powered it back up, and tried using the 370 as a plain old calculator keyboard/display unit — functionality which was known to work in the past. Sadly, there was no response to any keypresses on the 370. It appears that in the process of trying to figure out what was up with the timing circuitry, some other problems have cropped up.

Just to make sure that the 360E electronics package didn’t have a problem, a 360K keyboard unit was connected up to it, and it worked fine. So, the problem is definitely something new that has developed with the 370. It seems that I had made one step forward then taken two steps back.

This isn’t the first time that such a situation has occurred when working with old electronics like this. With equipment that is nearing 40 years old, there is much potential for problems. Sometimes just the physical shock of unplugging circuit boards can cause components that were marginal to fail completely. Sometimes no matter how carefully old circuit boards are manipulated, just the act of moving them can create other types of non-component-related problems such as solder joints that were perhaps weak to begin with suddenly failing. Such things are a simple fact of life when it comes to working with electronics that are this old.

While this is a bit of a setback, it isn’t a disaster. It just means that it’s going to take a little more digging to get to the bottom of the problems that this Wang 370 has. Of course, I will make update postings here as time presents itself to do more troubleshooting.

28-Feb-09 – 1965 Friden Competitive Analysis

Recently I received an EMail from a fellow old technology afficionado in The Netherlands, Frank Philipse, who had found an interesting document in a used bookstore where he lives. The document is entitled Electronic Calculators Report 1965. It was produced by Friden International S.A., in Berg en Dal, Holland. I have not been able to find out much about Friden International, but do know that it was a wholly-owned business unit of Friden Calculating Machine Co., and remained a relatively independent arm of Friden even after Singer bought out Friden in 1963. It appears that Friden International S.A. was involved in a lot of research and development work. I do know that a lot of development work on the Friden 5005 Computyper was done in Holland, as my Godparents’ business bought a 5005 Computyper from Singer/Friden, and a bunch of custom programming was done for the particular application they had. All of the programming work was done in Holland, and while the programming was being debugged, the Friden reps would spend a lot of time on the phone to the engineers in Holland who developed the programming.

The document that Frank found was clearly intended for internal use by sales and marketing people at Friden. It was written as a competitive comparison between the Friden EC-130 and EC-132 calculators versus other electronic calculators on the market in the mid-1965 timeframe. The document is quite comprehensive in its coverage, addressing competitive machines from IME, SCM, Olympia, Casio, Dero Research, Sumlock/Anita, Victor, Sharp, Canon, Tohiba, Oi Electric, Nippon Calculating Machine Co., Monroe, Olivetti, Philips, Wanderer/Nixdorf, Mathatronics, Wang, and Wyle Laboratories.

In reading through this document, there was a lot of great information contained within, and, for the most part, the comparisons were reasonably fair. While generally the comments were resonable, I sometimes found myself shaking my head at some of the “stretches” that were made in terms of how Friden compared their machines to their competitors. It was also quite interesting how some competitive machines were addressed in great detail, while others were simply glossed over with very basic comparisons.

An example of a competitive machine that Friden spent a lot of effort to review was the comparison between the SCM Cogito 240 (Yes — there was a Cogito 240..a machine without the Square Root function, though who knows if any survive today) and Cogito 240SR. They went to great detail in explaining the architecture and operation of these machines. Then, they went about ripping the machine to shreds when comparing it to the EC-130/EC-132. It was made very clear that the Cogitos were slower, harder to use, and in the case of square root, “archaic”. It is an interesting question to ponder: Why did Friden pick on this particular machine so intensely? Was it perhaps because it used a CRT display like the Friden 130/132? It is quite clear that Friden thought that their CRT-based display was a brilliant innovation. Perhaps Friden viewed SCM’s machine as a “copy” of theirs, making it more worthy of their ire than other competitive calculators with simple Nixie-tube displays or printers?

Their comparison of the “new” IME 84 RC (RC standing for “Remote Calculator”, a follow-on to IME’s brialliantly-designed first electronic calculator, the IME 84) was interesting. The IME 84RC allowed remote keyboard/display units to be plugged into the main calculator unit. This could mean that a main calculator could service a number of remote keyboard/display units. It isn’t clear to this day if the remote keyboards could be used simultaneously (like Wang’s later 200 & 300-series SE (Simultaneous Electronics) machines). The report commented that they thought that the idea of a remote calculator was oversold by IME, and also that IME was a “small company” that likely couldn’t compete in the market. While they may have been right about IME making too big a deal out of the remote calculator capability, it’s clear that the concept in general was viable, as Wang’s Simultaneous units were quite popular sellers, especially in educational and engineering environments.

The claimed that the Dero Research Sage 1 calculator “looked like a toy”, and didn’t really give much information about the machine. The report brushed the Sage 1 off as non-competitive because they considered Dero to be an insignificant player in the market. I wish that they had given more information about the Sage 1, as there’s very little information out there about this machine, though there were some interesting morsels of information that were used to update the Old Calculator Museum “Wanted” page for this machine.

They gave the Olympia RAE 4/15 (Olympia’s first electronic calculator) a pretty good review overall, but claimed that the Friden stack-based architecture allowed problems to be solved with less keyboard operations, a fact which is true.

They made no comparison between the EC-130 and the Anita Mk 10. They simply outlined the interesting aspect of the Mk10, which was its ability to perform calculations with English currency. In this part of the document, Friden International indicated that a similar report was done in late ’64 to early ’65 that addressed the Anita Mk 8 and Mk 9 machines, so apparently it was felt that there was no need to perform a comparison with the Mk 10. The tidbit of information here is that there’s an earlier version of this document out there somewhere — hopefully it can be found.

Friden commented that the miraculous (because it used Large Scale Integration (LSI) MOS integrated circuits) Victor 3900 was technologically advanced, but more difficult to operate, and rather expensive compared to its own machines. Interestingly, they didn’t seem to hammer on the Victor 3900 like they did the Cogito 240/240SR. It’s not quite clear why Friden didn’t appear to consider the Victor machine to be a real market threat, as Victor was a major force in the calculating machine market, and had a lot of experience with building high-quality mechanical and electro-mechanical adders and calculators.

A summary of Japanese competition was given in the form of a chart that outlined basic parameters such as capacity, math capabilities, cost, etc. No real in-depth analysis was done, but they did comment that the Sharp Compet 20 (no square root) and Compet 21 (square root) were the most competitive machines amongst the Japanese offerings, though still making it clear that the Friden stack-based math architecture was superior to any of the Japanese machines. They did indicate that the massive growth in the number of players in the electronic calculator business in Japan was something to be concerned about.

Comparisons were made between various printing electronic calculators on the market at the time, including the Monroe EPIC 2000, the Olivetti Programma 101, the Philips EL-2500, and the Wanderer Conti. They pointed out that having printed output was a competitive advantage in business applications over Friden’s CRT-based calculators, but made it clear that the noise made by the printers in these machines was a definite downside as compared to the silence of Friden display calculators. The report went into reasonable detail about the Monroe EPIC 2000, pointing out (something I didn’t know) that the machine used a similar stack-based architecture to the Friden EC-130. They underplayed the programmability of the EPIC 2000 as something that most users were likely not to be able to make much use of. They had little comment on the groundbreaking Olivetti Programma 101, but pointed out that delivery times were as long as six months after an order was placed. One can imagine that the capabilities of the Programma 101 were daunting to Friden to say the least. They also complained about the keyboard action on both the Philips and Wanderer machines, saying that they were “unreliable”.

A section on “Scientific” calculators included the Mathatronics Mathatron 8-48; the Wang LOCI 1 & LOCI 2 and the initial Wang 300-series (300, 310, 320) calculators; and the Wyle Laboratories Scientific.

They commented that the Mathatron was overly complicated, and that Mathatronics was too small of a company for them to be concerned about. An interesting tidbit was learned here in that they actually evaluated a machine called the “EMD 8-48″, which was a version of the Mathatron 8-48 manufactured under license by French company Electronique Marcel Dassault. I wonder if there are any surviving examples of this machine anywhere.

They had pretty high praise for the Wang calculators, pointing out the advanced mathematics functions that these machines offered. Their competitive stance against the Wang machines was that Wang Laboratories was a small company, and likely would not be a formidable competitor. Little did they know.

There wasn’t much information given about the Wyle Scientific, but they commented that they thought this machine was a prime example of a calculator designed by a bunch of electronics engineers who didn’t have much of a clue of the practical applications for an electronic calculator. They also said that “recent developments” would soon make a machine like the Scientific obsolete (perhaps they were thinking about the Olivetti Programma 101 when they wrote this statement?).

The unearthing of old documents such as this can give some really great insights into the mindsets of those deeply involved in the business of calculating machines at the time. Especially enlightening are internal documents that are targeted toward the sales and marketing staff, because they give a lot of editorial opinion relating to the originator’s attitides regarding their competitors and their guesses on the future of the business.

I will be putting this document online in the museum soon. Watch the Old Calculator Museum Change Log to see when it becomes available. For someone interested in old calculators, it is really a lot of fun to read.

17-Feb-09: Friden EC-130 Display System

I recently received an EMail from Mr. Jack Bialik that contained some very interesting information about the development of the CRT-based display system that ended up being used in Friden’s first electronic calculator, the Friden EC-130. All of the information contained in this posting is from Mr. Bialik’s memories of a project he was involved in at Stanford Research Institute in the early 1960′s.

Mr. Bialik obtained his BSEE from University of Michigan in 1950. After graduating, he worked at Consolidated Vultee Aircraft Corp. (CONVAIR), where he was involved in development of a display system utliizing CONVAIR’s Charactron display tube technology. Joseph McNaney of CONVAIR invented the Charactron tube in 1949, but the production operations were later transfered to Stromberg-Carlson (S-C) by General Dynamics, the parent corporation of (among others) CONVAIR and S-C. In late 1955, Mr. Bialik left CONVAIR, and joined Stanford Research Institute (now known as SRI International), a non-profit research and development organization founded in Menlo Park, California, in 1949. The Old Calculator Museum wishes to thank Mr. Bialik for sharing his memories.

In the latter part of 1961, SRI was contacted by Friden Calculating Machine Company’s VP of Research and Development, Mr. Larry Robinson. Robinson requested a proposal from SRI’s Computer Lab to design and develop a prototype transistorized CRT-based numeric display system that could display four lines of 27 digits on a small CRT display. Friden’s stated intention then was to use the SRI’s research efforts as the basis for producing an electronic display for an electronic calculator that Friden was planning to build. Friden’s requirement for such a display for this calculator was defined by the desire for the machine to be able to display the entry register, the result register, and temporary registers used to hold intermediate results of calculations. Existing display methods (Nixie or Pixie tubes) would require way too much space, power, and expense in order to display a similar amount of data. The use of a CRT display would provide a much more compact and efficient means to display this quantity of information.

Mr. Bialik, and his immediate Supervisor, Milton B. Adams, wrote up a proposal for the project that Friden accepted. Work on the project began in late 1961. A five-man design team was put together, with Mr. Bialik as the Project Leader and architect; Dave Condon and Dale Masher performing design work (logic and circuit implementation); Don Ruder to develop a separate testing system to drive the display subsystem; and Bill Stephens to fabricate the designs.

In early 1962 , SRI delivered to Friden three hardware copies (and associated documentation) of an engineering prototype display system that met the requirements established by Friden.. The display system contained four plug-in circuit boards that contained all of the circuitry to implement the display system, including the high voltage drive for the CRT. The prototype units were packaged in an aluminum housing with a viewport that allowed the face of the CRT to be seen, as well as house the electronics and power supply for the display system. Also included in the deliverables was a “calculator simulator”, a device that would allow digits to be entered into a keyboard and displayed on the display subsystem. The simulator device provided a means to test and troubleshoot the display system, and also to demonstrate that it indeed operated. The calculator simulator device was not a calculator — it could not perform any arithmetic. It only provided a means for entry (via a keyboard); storage (via a small magnetic drum); and control logic (transistorized circuitry) that would provide a source of data for the display system to display. Along with the hardware, all of the design information, engineering notebooks, and any other data related to the project were turned over to Friden when the project was completed and signed off.

Along with all of the work on the project itself, a patent (US Patent #3430095) on the principles of the display system and the “calculator simulator” was filed. It isn’t clear if SRI drafted the patent application for the concepts of the display system on its own, or if this was part of the arrangement with Friden. What is known is that because the work done by SRI was an exclusive “CLIENT CONFIDENTIAL” contract with Friden, once the patent was approved (not until February of 1969), SRI assigned all rights to the patent to Friden Calculating Machine Co. The patent lists Mr. Bialik, Mr. Masher, and Mr. Stephens as the inventors, but makes no reference at all to Stanford Research Institute.

The display system worked as required, and Friden appeared pleased with the results. The design of the display system was used pretty much un-modified from its SRI-designed form in various calculator prototypes. An early prototype electronic calculator, patented by Friden (US Patent #3474238), was based on a magnetic drum memory system, very similar to that used in the “calculator simulator” developed by SRI. Diagrams and text in this patent are very similar to those listed in the patent for the display subsystem and “calculator simulator”. Later patents from Friden outlining design prototypes that led to the development of the EC-130 also used much of the material in the original patent with little changes.

Although more research needs to be done, it seems pretty clear that in the early stages of brainstorming their ideas for an electronic calculator, Friden grappled with issues relating to how they were going to display the working registers of the machine that they had envisioned. One of the early prototype calculator patents filed by Friden indicated that it was considered very important that the calculator be able to display all of its working registers for the operator to see. As a result of this requirement, and limitations with existing numeric display technology, Friden had to look outside the company for design expertise in display systems technology. While it’s clear that Friden had internal resources skilled in the art of digital design, perhaps the “analog-ness” of the design requirements to generate a CRT-based numeric display required skillsets that didn’t exist in-house., This is probably why Stanford Research Institute’s Computer Lab was hired to do the design.

While the development of the display technology certainly played a significant role in making the EC-130 an early reality, the display system was only a part of what was needed to make a complete electronic calculator. It appears that much of the display system concept developed at SRI, along with some concepts from the “calculator simulator” (including basic transistorized logic gate designs) were used by Friden in the development of the EC-130. However, clearly the internal design work that went on at Friden to put the “brains” behind the display system was by far a more challenging task.

This commentary is in no way intended to take away any of the significance of Friden’s engineering effort in the development of the EC-130. It is, however, an interesting new tidbit of inforamation to add to the story of the development of Friden’s first electronic calculator.

06-Feb-09 – More Busicom 161

The Busicom 161 calculator chassis donated to the Old Calculator Museum arrived Tuesday (2/3) morning. The box it was packed in looked a slight bit worse for the wear due to handling during shipping, but structurally, the box looked OK.

The machine was double boxed, which is one of the best ways to ship old calculators (the best way being custom-made conformal foam packing). The machine was cushioned by styrofoam packing “peanuts”, another good thing, however, it’s usually a good idea to first seal the machine in some kind of bag (preferably an anti-static bag) to keep the packing material from working its way into every nook and cranny — especially in a machine like this that is a bare chassis, without the cabinet. It took about 1/2 hour with long handled tweezers to pick all of the packing material out from between circuit boards, under the keyboard, and in various other cavities in the machine.

The first order of business, after harvesting the peanurs, was to give the machine a complete visual inspection once all of the packing material was removed. It was noted that one of the discrete neon lamps that are positioned between the Nixie tubes as decimal point indicators was missing. The wires for the lamp were sticking out of the circuit board, but the lamp itself was missing. Referring to the photograph of the machine placed in the eBay auction showed that the lamp wasn’t there in the auction posting, so it wasn’t missing as a result of shipping damage. This isn’t a big deal, as it likely can be replaced. The chassis was turned upside-down, and the glass neon tube fell out from inside the machine. Apparently somewhere along the line, the indicator was broken, probably as a result of improper handling without the cabinet in place, and it fell down inside the machine.

The next step was to very carefully pull out each of the 41 logic circuit boards. There are 42 logic circuit boards in the machine, but one of them isn’t removable. It contains the Mitsubishi-made 16×16 magnetic core array, and it is hard-wired into the backplane. Why this board is hard-wired is beyond me, – many machines of similar design use plug-in core arrays. It is interesting to note that the IME 84, upon which it appears the Busicon 161 was patterned, also has a fixed circuit board for the core memory array. Anyway, all of the logic boards were individually carefully withdrawn from their backplane connectors.

As discussed in the original posting about the Busicom 161, the museum’s existing machine has severe problems with the edge connector sockets losing their structural integrity. It was strongly hoped that this chassis didn’t share the same problem. Unfortunately, as the circuit boards were removed, it was found that of the 41 sockets, six of them suffer the same kind of problem.

The problem manifests itself by cracks developing in the plastic-like material that the socket contacts are encased in. The socket contacts are gold-plated, and look somewhat like a “Y”, with the open part of the “Y” being where the card edge connector is inserted. Each connector has 22 of these contacts. Once the plastic material cracks sufficiently, the tension that holds the contacts in place is released causing the contacts to become mis-positioned, and also to lose the spring tension that keeps them in contact with the gold-plated fingers on the wire side of the logic circuit board.

Given the problems wtih the backplane, it was not safe to try to power up the machine with the circuit boards in place. But, it was possible to check out the power supply. The damaged backplane connectors were carefully inspected to make sure that none of the contacts were shorted, so that when the machine is powered up without the circuit boards, there’s no chance of short circuits. The Nixie tube display subassembly, and the keyboard subassembly were removed. Both subassemblies connect into the backplane wiring with high-quality connectors, allowing these units to be easily removed and serviced. Unfortunately, the power supply is hard-wired into the backplane, meaning that some disassembly is required in order to look at the power supply circuit board. Once things were taken apart enough, the power supply board was found to conveniently have nomenclature on it identifying the various voltages. The power supply makes +5, -12, and -5 volts for logic supplies, and +85 and -85 Volts for powering the Nixie tube displays. The power switch for the machine is located in the keyboard assembly, and thus the wiring for the power switch had to be traced and a jumper fashioned to plug into the socket that the keyboard plugs into, in order to simulate the power switch being “on”. Three digital voltmeters were connected up to the power supply, and the power cord was plugged into a Variac, and the voltage slowly ramped up. There were no signs of any trauma as the mains voltage was ramped up to 50%, then slowly up to 75%. The digital voltmeters started to register voltages. Once the mains voltage was at 100%, the +5V supply read +5.31V, the -12V supply was at -13.21V, and the -5V supply was at -5.89V. The voltages were all a little higher than expected, but this is liekly because there was no load on any of the power supply voltages. The Variac was turned off, and two of the DVM’s connected up to the +85 and -85V Nixie tube power supplies, and the machine powered back up again. The +85V supply was running at almost 89V, and the -85V supply was running at just over -90V. These voltages aren’t as critical as the logic supplies, and aren’t actively regulated. Transformer windings are simply rectified and filtered, so some variance in the output voltages is to be expected. Lastly, the machine was again powered off, and the oscilloscope connected up to the logic supplies to measure ripple, to make sure the power supply filter capacitors were OK. All of the logic supply voltages had only slight (1-2 millivolts) of ripple, all within safe boundaries. With all of these measurements performed, the power supply of the machine seems to be in good health after all these years.

Speaking of years, this 161 appears to have been made at very close to the same time as the original 161 in the museum. Transistors are all coded with dates in the range of the 2nd week in 1969 to the 5th week in 1969, while the original 161 has date codes that are just a few weeks later, with the latest date codes listed being in the 6th week in 1969. In a rather silly move, Busicom put the serial number tag on the back surface of the upper part of the cabinet. The upper part of the cabinet on the recently donated machine was missing, thus, there’s no way to identify the serial number on this machine. While disassembling the machine, I looked high and low for any hints of a serial number stamped or written in other locations within the chassis, but none was found. This is rather unusual given the price of machines of this vintage (frequently $1000 or more, which was a lot of money in 1969), many manufacturers put the serial number on a fixed part of the machine that was not easily removable, and also had markings inside the chassis that provided secondary identification of the serial number to aid in identifying a machine if it was lost/stolen.

It is going to take some time to figure out a stragegy to replace the edge connector sockets that are bad. Experience trying this with the other Busicom 161 proved to be futile. That time, the connectors were replaced with the backplane in place. This involved very carefully separating the dense wiring to clear it away from around a failed edge connector socket (horribly difficult because the backplane wiring is very tightly laced into a big bundle of wire), carefully desoldering the wires to the bad connector, putting in a new connector, and then soldering the wires back to the new connector. This proved to be nearly impossible due to the density of the backplane wiring. A different approach is going to be needed to replace the faulty connectors on this machine. Fortunately, the connectors used are standard 0.156-spacing 22-pin sockets, easily available through any electronics supply outlet. The edge connector sockets in the 161 are held in position by rectangular holes in the bottom of the circuit card guides that are screwed into the chassis. There are bosses on each end of the edge connector sockets with a hole through them that would allow the connectors to be screwed into a circuit board or chassis to hold them in place. The screw holes are not used in the 161, but these bosses fit into the rectangular holes on the circut board edge guides on each end of the connectors to hold each connector in place. If the card guides are removed from the chassis, this would free up the edge connectors to “float”, allowing the backplane to be worked on in a much easier fashion. The only support for the edge connector sockets at this point would be the backplane wiring itself. This is likely that strategy that will be used to try to safely replace the damaged sockets. The real difficulty with any means to try to replace the connectors is that the backplane wiring uses only minimally color-coded wire, and due to age, heat cycling, and other factors, the coloring on the wire insulation is sometimes very difficult to make out. There’s no schematic or service documentation that I’ve run across for the 161 (if anyone knows of any such documentation, I’d love to hear from you), so it means that very careful observation and documentation of the wiring will have to be done. This will rquire a lot of digital photography at close-quarters, a lot of time with bright lighting and a magnifying glass, and meticulous note-taking. Keeping all of the wiring sorted out to assure that it all goes back together again with the correct connections is going to be absolutely critical. No room for any errors here.

I need to get hands on replacement connectors, which is something I hope to do sometime soon. Once I have them in hand, and have been able to take things apart enough that I can test my method for repair, I’ll make a new post here letting everyone know how its going. In the meantime, I plan on taking the original machine and taking photos of it (though it’s certainly not operational), and begin the process of creating a museum exhibit for the Busicom 161. The goal of the Old Calculator Museum is to have fully operational machines, but for the time being, the Busicom 161 exhibit, when I put it online, will be one of the few exhibits where the machine shown isn’t operational. But, over time, I hope to be able to get a fully-operational machine. Betweent he two machines, there are plenty of spare parts that an operational machine can be made, assuming I can get through the backplane repairs without causing more problems or, worse yet, irreparable damage.

Thanks for reading.