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My 2¢: I feel like you'd have an easier time reverse engineering the card if you assumed the 65C02/IWM-connected side of the Gemini was largely the same as a normal IIe, and then connected a logic analyzer to the LC PDS side to see how the LC pokes and prods at the IIe hardware. Decapping the...

It's definitely still possible that it could be a trace issue, but the impression I got from his first posts was that the board is clean and in fairly good shape (besides the fact that it doesn't work, of course ;)).

Could also just be that the chip died of old age. Hope it's not too inappropriate to ask this, but @Elemenoh would you have any interest in selling the card with the bad chip on it for parts?

Like @Elemenoh said, looks like the G2 needs adjustment on that analog board, not the same kind of gray screen. My boards' DFAC-related symptoms looked much more like the photo @lfletche posted. Since you're getting a black screen, you can probably rule out both the DFAC and CUDA at this point...

Being able to rule out the ROMs too is nice. Last thing I'd try is replacing the 74LS245 at U10. The first things that come to mind for why you wouldn't hear death chimes after an NMI at this stage are a.) the CPU can't write to the Spice IC, where sound is generated before being filtered by...

ISTR that the thing about the grounding springs stems from a video by Adrian's Digital Basement in which he tried running an LC575 board in a Color Classic chassis without the RF shielding, resulting in audio issues. At any rate the springs are not critical on the original CC motherboard. My CC...

Personally I doubt it, there tends to be a fair bit of variation in these readings between individual boards. A surefire way to test would be to measure the voltage on that pin: after pressing the power button on the keyboard, it should read 0V for a little under one second, then jump up to...

The fact that the system powers on to some degree (fan/drive spinning) indicates that the CUDA, referred to here as the EGRET, is likely fine. Would be a different story if the system wasn't responding to the power button on the keyboard at all. The motherboard grounding springs should have no...