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.
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.