Today we attempt to repair and refurbish a Monromatic CSA-8 electro-mechanical calculator from the 1950s-1960s. At the moment addition and subtraction don't update the accumulator among othet issues, I hope just from seized gears. ⁨⁩ ⁨

I decided to start by fixing the shift mechanism, which stutters when shifting left. I'm hoping resolving that may also resolve some of the other issues. I was able to locate a service manual for a similar calculator which has some decent diagrams.

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Sound ⁨⁩ techniques can be applied to all classes of problems, and I'm using the same approach I wrote about in DevOps Troubleshooting. I identified an issue (shift mechanism) and to narrow down the cause I now need to study and understand how this mechanism works.

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I was able to fix the shift mechanism with a few adjustments and while I was at it figured out what was wrong with the main accumulator so now addition and subtraction work. Next up: multiplication.

@kyle
Wait, what was wrong with the main accumulator? You're not gonna leave us hanging here are you? Was it seized gears?

@JohanEmpa Alignment between the top carriage and the bottom gears from the keyboard! Repairing shifting made the misalignment more obvious. It still isn't perfectly aligned though (falls out when left shifting during division for instance) so more tweaks are needed.

@JohanEmpa Actually if you look at the picture of the rear of the calculator you can see a metal cylinder that extends down into a large worm gear. That is what controls where the carriage is when shift stops occur and you can adjust it via screws at the top to shift it left and right.

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