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70 year old radios aren't plagued by low-ESR electrolytics going out of wonk in a 20 year period. The failure modes are quite different.

The 53C80 has its DMA pins plumbed in, at least on the SE and following machines. Not sure about the Plus, I don't have the board handy.

IIRC it's the PHY that fails. What sits on the daughtercard.

Anytime!

Done https://github.com/GeorgeRudolf/SCAterm

I had made a bodge-on PCB that added termination to existing adapters for @Phipli - but I don't think I posted it anywhere public. I might do that.

I have a dead board with a potentially good transformer, and as such, a machine needing a board, but I suppose shipping the spare transformer might not be worth it.

They're custom parts. Essentially irreplaceable, short of measuring turn count and rewinding a new transformer over the same core.

Theoretically how this should work is: TRICKLE_D (TrickleDetect) is an input on Cuda - it senses that the machine is energized because the power supply has raised the 5V_TRICKLE line. It presumably won't attempt to power on if that is not detected, or at least I don't think it generates a...

Cuda isn't exactly a complex beast. The pinout is there and it never changes between machines. I don't think it's got anything shorted, else the machine probably wouldn't operate without the battery. Really, the easiest way to go about this is remove 0120 and see what sort of consumption you get...

Nope, that's a custom part. 0120 is shorthand for 343S0120. You could theoretically replace it with some other battery voltage monitor IC, but that would need a bodge.

To bake you'd remove the glass from the PCB, and hardwired connections wouldn't be an issue in that case. Replacing would mean finding one without tunneling :P But yeah, I hear you.

Mounted to little pieces of flex ribbon that connect the glass to a small PCB, under the metal bezel. That's an extremely delicate area.

Not a datasheet, but as close as we're ever gonna get to one, I think. The signals are the same as always. CL1, CL2, FLM, 8 bits of data per upper and lower half. You can kinda ignore the MQ200 columns.

Either that, or a continuity issue in the PCB holding the drivers.

The IIsi should already have termination power. At least on the external port it is supplied via D1, L1 and F2 - it stands to reason that the internal is connected the same way. If not, run a jumper from the DB25 pin 25 to pin 26 on the 50way header.

That'll be an obsolete part. I'm guessing pitch is 1.25mm for that end - Molex 0039532264 is not ZIF but might've worked. In any case, being in your situation, with a bad connector and a bad ribbon, what I'd do is hardwire the panel to the interconnect board using something like 80way IDE ribbon...

Got a panel model? Sometimes we might luck into finding a datasheet that's close enough.

Both bricks on there are transformers and part of the multi-rail SMPS that is the power board. I would try finding a way to bench-test this - a failure could well cook the machine. One open via is enough. Ideally you'd remove those with hot air. Even more ideally, you'd find a replacement power...