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Ha, nope... I just had similar symptoms when I had a grounding issue in a 140, so it sounds familiar. You're right about the diode originally being a zener and present for reverse polarity protection... I have a vague memory though of a non-zener replacement possibly allowing reverse leakage...

You can buy 6V caps, but they're super unusual. And not available afaik at this capacitance or form factor.

Had to look it up - apparently cap V's are 6.3 because it accounts for the 25% safety margin over 5V: https://www.eevblog.com/forum/beginners/capacitors-why-6-3v/

Documentation somewhere a long time ago... '22' is the capacitance in µF, '6' is the voltage (for some reason always 6.3), the 'S' is the series (I think can be either A or S), then the last line is manufacturer codes I think? Not relevant to the values though.

22µF, 6.3V

Hm. It sounds possibly like a grounding issue, or something is tripping ground detection... which diode did you replace with the IN4004?

Yeah I saw the offset pin, but what I can't see is what it's connected to. From one of the other images, all I see is pins 1 and 3 having traces, which make sense given this is mains input (there's only going to be GND and 120V)... but I could be wrong about the other two. The Meanwell has a...

Oooooh - I see, I think that's the mains input connector for your PSU... it looks to me like that connector only uses pins one and three but I can't see the whole thing. I can't imagine what that offset pin is for - is it connected to anything?

For the +5V/+12V output? I don't know if it has a name, but any 4-position assembly with this connector should work: https://www.digikey.com/en/products/detail/molex/0022013047/26435 Edit: here's the datasheet for the Meanwell: https://www.meanwellusa.com/upload/pdf/PD-25/PD-25-spec.pdf

Hm. Does that mean the modem connector could be used for an internal wifi serial modem emulator?

Whoa - sounds like you were connecting straight to mains voltages. The board is only supposed to receive +5V and GND, so hopefully everything is ok... sounds like it is. In this case, I believe you should be tapping +5V and GND from the logic board, which should be easy. I have a couple of...

Agree re: System 6. Also worth consideration: https://androda.work/product/macintosh-portable-7-megabyte-ram-card/

Either that or remove the battery when you're not using it (and also remove the 9V). It really depends on how long you're keeping the thing on the shelf. I don't use mine a whole lot (once every few weeks), so I don't have a 9V in it, and I don't put the battery in it until I use it. I don't...

SAM's should have what you need: https://archive.org/details/Sams_Computer_Facts_Apple_IIc/page/n43/mode/2up

Wow, this is impressive, adventurous stuff. Thanks for leading the charge and sharing your experience. More research to be done...

I also would like to know... if you find out, please update us!

For trace repair, I just use copper strand wire salvaged from an old power cord... it's just straight-up copper wire very fine gauge (couldn't say exactly), works well enough for those small little bridging repairs where you're recreating the trace or reconnecting a via. But for longer bodges, I...

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That's my understanding as well - not so much that the higher amperage damages chips, but that over time Q16 will burn itself open allowing 6V+ and worse (i.e. 7.8V) through to the PMGR etc. instead of the regulated 5.2V... but how exactly the mosfet fails in this circumstance is unclear to me.