Archive for January, 2009

29-Jan-09: Wang 360SE

January 29, 2009

Today I had some time to look into the Wang 360SE that was recently donated to the museum.

Visual inspection was the first order of business.  First, the cover over the backplane was removed so that a complete visual inspection of the backplane and power supply circuit board could be performed.  The backplane in the 360SE is a hard-wired affair.  Wang used a unique method for wiring the backplanes on these machines that used special edge connector sockets with long rectangular tail pins on the backside that special clips attach to.  The clips are soldered to the individual wires in the backplane wiring harness.  The clips visciosly grab the tails on the edge connector sockets to provide connectivity between the various edge connector sockets.  Intuitively, this method doesn’t seem like it’d be very good in terms of long-term reliability, but amazingly, it seems to work very well.  Even though the edge connector tails and the clips are made from what appears to be a tin alloy, the connectivity this system provides seems to be very relaible, even after 40 years.

Looking over the backplane carefully showed no signs of any loose connections or broken wires.  The power supply circuit board looked as if some of the components (mainly rectifier diodes) had been replaced at some time during the machine’s life.  The machine’s service tag did not indicate anything of these repairs, so it is likely that these repairs were not done by a Wang service technician.

The backplane cover was replaced, and the cover over the Logiblocs was then removed.  All of the Logiblocs were then carefully pulled from the sockets so that all of the edge connector socket fingers could be inspected, as well as checking the edge connector fingers on the Logiblocs for corrosion.  The edge connectors were all in good shape, and there was only light corrosion on the Logibloc fingers, which were all cleaned with a contact cleaning solution.  Each Logiblock was also inspected to make sure there were no sign of obvious problems, and all looked good.  The core memory board was inspected under a magnifying glass to check for any broken wires in the core array, and no problems were found.

The power supply transformer and large computer-grade capacitors were visually inspected, and looked good.  The line voltage fuse was checked, and it was found to be good.  Without power connected, an ohmmeter was placed across the power supply hot and neutral prongs on the plug, and the power switch turned on to check for too little resistance, which could indicate a shorted line filter device, or the mains winding in the transformer. The ommeter showed about the same resistance reading as the known good Wang 360SE already in the museum.

The power supply of the 360SE generates +11V and -11V, along with 230V for drive of the Nixie tubes on the keyboard/display units.  With all of the Logiblocs removed, it was possible to power up the machine and check the power supply voltages.  The 360SE electronics package was plugged into a Variac, and the voltage very slowly raised up to full line voltage, while monitoring the +11 and -11V supplies using two digital voltmeters.  It became apparent as the line voltage neared 50% that the power supply wasn’t doing anything.  The +11V and -11V DVM’s showed +0.000 on their displays.  As I ramped the voltage up to full line voltage, there still was no output at all on either of the logic power supplies.   Clearly, there’s something amiss with the power supply, that will require more digging to sort out.

There are two thermally activated "pop out" circuit breakers that provide protection for the +11V and -11V supplies.  The first thing to do was check them.  Visually, they weren’t popped.  They were both checked wtih an ohmmeter, and had full continuity.  Unfortuntately, the problem was not going to have a simple solution.

I ran out of time to work on the machine any further during this session.  The next step will be to check the transformer secondary voltages with power applied to see if the transformer is working properly.  If a problem is found with the transformer, finding a replacement is going to be difficult.  Any replacement would have to have the proper primary and secondary windings, as well as be very close to the size of the original, as the transformer is pretty tightly packed in the chassis.  If the transformer proves to be OK, then the problem is likely somewhere in the circuitry that takes the AC voltages out of the transformer, rectifies it to DC, filters it, and then regulates it to the proper supply voltages.

I’ll write about further digging into this in a future blog entry.

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28-Jan-09: Busicom 161

January 28, 2009

Apologies for delays in posting to the blog — things have been somewhat chaotic around here.

Some more work has been done on the Wang 370/371, but it needs to be written up and posted.  Hopefully I’ll get to this soon.

This posting is about a recent development relating to a Busicom 161 electronic calculator. For background, the Busicom 161, introduced in July of 1966, is the first electronic calculator sold by Japanese calculator manufacturer Nippon Calculating Machine Co. (NCM).  NCM had made a big market for itself in the Japanese market by making wonderfully compact and reliable hand-operated mechanical calculators that could replace the soroban (abacus).  With the advent of the electronic calculators, first by Sumlock Comptometer/Bell Punch (the Anita C/VIII) , followed by others, NCM felt that their corner on the market for small mechanical calculators could be at risk.   As a result of this concern, NCM embarked on a program to develop an electronic calculator.  The Busicom 161 is the result of their efforts. NCM created a new business subsidiary called Busicom (Business Computer) that would be the trade named by which NCM would market their electronic calculators.

Rumor (not well substantiated at this point) is that the design of the Busicom 161 was based on information gleaned from reverse-engineering a calculator made by Italian calculator maker, IME (Industria Macchine Elettroniche), the IME 84.  The IME 84 was a brilliantly-designed machine, implemented with all-transistor logic, magnetic core memory for register storage, and Nixie tube display. There are claims that the IME 84 was the first electronic calculator to use magnetic core memory, but this assertion is incorrect, as the Mathatronics Mathatron calculator holds this historical distinction.

The Busicom 161 may share the same architecture of the IME 84, but its implementation is much less sophisticated. The IME 84 has a much higher component density, with the entire machine housed in a compact, low-profile desktop package. The Busicom 161, in contrast, is comparatively huge. It takes up about the same amount of square inches of desk space, but it is much taller. The circuit boards in the 161 are very simplistic, using low-component density (the most complex boards have 20 transistors on them), with circuit traces only on the back side of the board, and single-sided edge connector fingers. The 161 uses a total of 42 circuit boards, arranged in three rows of 14 boards each, stacked vertically in the chassis, which is the reason why the 161 is so tall. The machine has a capacity of 16 digits, with fixed decimal of 0, 1, 2, 3, 6 or 9 digits behind the decimal point. The Nixie tubes display the digits zero through nine, and decimal points are indicated by discrete neon lamps situated between the Nixie tubes. The 161 has a single accumulator-style memory register, and one-key automatic square root. Transistors used in the Busicom 161 are made by Mitsubishi, using standard 2S-series silicon transistors.

NCM/Busicom holds a special place in history. In the late 1960’s, Busicom engineers had developed a design for a complex calculator chipset that could be configured to perform the functions of a large number of different calculator applications. Busicom contacted fledgling integrated circuit memory manufacturer Intel, to see if they could fabricate the chips that Busicom had designed. Intel’s engineers looked at the complex nature of the chipset, and decided that it would be more efficient to develop a small programmable computer on a chip that could be programmed to perform whatever operations a calculator designer required. Intel took this idea back to Busicom, and while Busicom management and engineers weren’t initially impressed by the idea, and instead pushed back at Intel to simply fabricate the chips as originally specified, Intel’s engineers had developed a breadboarded prototype of a simple calculator based on the idea, and this convinced Busicom that this may well become the future of electronic calcualtors. Busicom negotiated an exclusive contract with Intel to produce the programmable processor, which historically became known as the first commercial microprocessor, the Intel 4004. Intel also developed support chips that provided read-only memory, random access memory, and peripheral interfacing chips. Busicom and Intel jointly developed a business-oriented desktop printing calculator that Busicom sold as the model 141-PF — the world’s first microprocessor-controlled calculator, introduced in October, 1971. Sadly, the Japanese economy went into a recessionary period during the early 1970’s, and in spite of the technological triumph that Busicom 141-PF represented, NCM/Busicom started to suffer financial problems. Intel saw an opportunity to get out of the exclusive agreement with Busicom for the 4004 microprocessor and support chips, and a deal was negotiated to allow Intel to sell the microprocessor to other customers just a month after the 141-PF was introduced. This development led to Intel further developing its microprocessor business, leading to the Intel 8008(April, 1972), and then, the 8080(April, 1974), the microprocessor chip that truly ushered in the beginning of the personal computer revolution. By February, 1974, Busicom’s financial woes prompted it to file for bankruptcy. In November of ’74, NCM/Busicom ceased operations, making the company the first major Japanese calculator manufacturer to succumb to ongoing shakeup in the calculator industry that resulted in many calculator makers getting out of the calculator business, or going out of business altogether.

Fast-forward to more recent times. A while back, the Old Calculator Museum managed to acquire a complete Busicom 161. It has not yet been documented in the museum because the machine needs restoration before it can be exhibited. The main issue with the machine was that the edge connector sockets in the hand-wire backplane were disintegrating. It isn’t known if this is endemic to the material used in the connector sockets in the Busicom 161 in general, or if this is a malady suffered by this particular machine due to some kind of environmental conditions during the machine’s lifetime. Appropriate replacement sockets were found, and a number of the original sockets that were in the worst condition were replaced. This operation was extremely tedious as the wire density in the backplane is high. The power supply was checked out to be OK, and once the connectors were replaced, the machine was powered up, but alas, it doesn’t function properly. Since then, more edge connector sockets have started to fail, meaning yet more connector replacement must be performed.

Busicom 161 Backplane Wiring

Now, to the present. About a week ago, a frequent donor to, and good friend of the Old Calculator Museum, sent an EMail indicating that there was an interesting looking calculator chassis up for auction on eBay. I checked it out, and realized right away that it looked very familiar. The machine at auction was a complete Busicom 161, minus it’s cabinet. In further EMail dialog, this friend indicated that they would be willing to bid to win the calculator, and then donate it to the Old Calculator Museum. The bidding went well, and now the Busicom 161 chassis is on its way to the museum.

It is hoped that the soon to be received chassis will have backplane connectors that are in good shape. The goal will be to try to get a fully operational machine, either by getting the chassis up and running, or by mixing and matching parts to get a working machine going.

Watch this blog for more information on this project.