Apple IIc restauration

[pixelpusher]

I recently bought an Apple IIc in not tested condition for an attractive price. The pictures didn’t look too bad, but it turned out to be a project to sharpen my restoration skills.

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While text and images showed a broken plastic of the top case, there was more (e.g. a two fine cracks on the top case and some loss of plastic on the lower case due to unsuccessful attempts to pry the case open…).

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Also, when the parcel arrived, there was some rattling (despite the computer itself well bolstered) - turned out half of the case connections were ripped off too.

Cracking the case open..
For those who don’t know, the official Apple guide is to remove the six screws holding the case together - but not the drive screws, making sure the handle is extended, pointing to the floor and letting the handle hit the floor from a few centimetres. Depending on how often the case has already been opened, letting the handle hit once or twice the floor will be enough to open the case without breaking anything (that hasn’t already been broken).

Once open it showed several plastic parts ripped off from someone trying as well as some missing parts (e.g. braces for the case connections that I rebuild with a bit of ABS).

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and after sanding:

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The worst part however was the left part of the lower case missing border in which the top case rests in. This longer section needed to be rebuild. ABS + acetone time…

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The electric side…

While the the cases were curing, it was time to have a look at the mainboard and PSU.

Instead of the original external PSU (which delivers 15V DC to the internal converter, that creates +/i12V and +/-5V), I connected a modern USB-C charger with converter module. When turned on, the USB-C voltage immediately dropped to zero, indicating a short in the internal PSU of the IIc.

Diagnosis revealed that the NPN power transistor was shorted. So, time to replace it and with I also replaced the electrolytic capacitors and some of ceramic ones (that are connected/close to the NPN transistor). Adding some RTV silicone to the bottom of big capacitor to hold it in place (I couldn’t get that large one in an axial variant) and now we’ve a working PSU.

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However the machine still wouldn’t boot. Having a newer ROM (4.x) version allowed for easy diagnosis though: One of the RAM chips being bad. Replace that too and voila, we finally a booting machine.

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Next steps...

will be to work on the visible scars on the case (my ABS didn’t match the case color) and also trying match the texture of the original plastic. I think I’ll try something with molding silicone and apply that with a little bit of solvent to the surface… (anyone already tried that?).

[HigashiJun]

Nice repair !