We fixed LGR's gorgeous calculator (Patreon)

You might have seen LGR's video about the Dictaphone 1680, née Sanyo ICC-0082 calculator, at the time the smallest battery powered calculator:

https://youtu.be/Sq_GFKpPhnY 

LGR is a great channel that reviews vintage personal computers with an eye on gaming, with great style and a unique soothing appeal. Kind of the opposite of my channel ;-).

But alas, Clint's calculator did not work, and he asked if anyone could help him repair it. We reached out, and he sent us his precious calculator.

And here is the Dictaphone 1680 in my lab, which is a rebranded Sanyo ICC-0082 from Japan. Unlike my FACIT 1131 lurking in the background (itself a rebranded Sharp Compet), the Sanyo's amber display is not quite made with Nixies, but with seven-segment gas discharge tubes. It's sort of a cross between a Nixie and a 7-segment display, a predecessor to the lower voltage VFDs, and much more beautiful in my opinion. Sanyo made their own tubes, and called them Eightrons. 

But unfortunately, these beautiful Eightrons did not quite work properly. Some segments and even entire digits appear to be missing.

We were very afraid that something might have gone wrong with one of the the four LSI chips that are at the heart of the machine. These were made by Sanyo under license from General Instruments. They look so eerily similar to the Rockwell chipset made for the Sharp QT-8D Micro-Compet that I wonder if they are related.

After a long search, I was able to dig some information about the chipset from an obscure forum post about a different machine. And it was in the form of two dozen pages of incomprehensible diagrams, with only cryptic symbolic formulas, tables and diagrams, worthy of an Indiana Jones riddle. And not one single sentence of explanation. Which of course did not stop Master Ken, who managed to crack the hieroglyphics in a matter of days.

But we sure hoped the fault would be in some of the power supply or segment driver logic, which involves a bunch of transistors.

We started instrumenting the calculator, and were comforted that the correct drive signals seemed to be coming out of the ICs.

At some point, we got really scared that some of the tubes were not firing and might be dead. These are nearly impossible to find, being only made by Sanyo. 

I don't want to spoil too much before the video, but after some acrobatic repairs, we prevailed. Look at all these glorious glowing segments. All of them!

The calculator actually uses 16 digits, which you can display in two halves of 8. This was really worth saving.

And as a bonus, Master Ken reverse engineered the whole machine, so if an IC dies in the future, it should be theoretically possible to replace it.

I have a few more business trips coming up that are slowing my video output, but please be patient with me, they will eventually come out!

Marc