First post, by scruit
I was trying to replace the CP-3044 HD with an SD-IDE or CF-IDE adapter and every time I plugged in the adapter and powered the machine on I got a black screen no-start. Even other period HDs had the same response.
With the working HD connected (keyed by the blind pin) I did some oscilloscope traces of the ide legs under the HD (using the physical key as a landmark for picking which pin to 'scope). It showed normal-looking data/address lines but some pins were inverted, like the -reset line and gnd/5v showed wonky results. Then I suspected a black-screen dead could be a short, but not ALL of the devices I tried could be shorted, right?
Long story short - The IDE header on the motherboard is the wrong way around. And it looks like they used a drive with no shroud around the connector with a blind pin to key it instead.
The header on the motherboard has the physical "key" in the wrong position. The physical key and the blind pin are at odds with each other.
Look at this pic... Bottom left... https://i.imgur.com/VQS5LGj.jpg
This pic was taken during disassembly, prior to disconnecting things... And it worked in that configuration.
The #1 silkscreen "above" the pin does not match the red wire BUT the red wire goes the the #1 pin on the HD.
EDIT: WAIT A SEC - That's the FDD, 34 pins. THAT is reversed too?!
So, the fix was to take a throwaway IDE cable, cut the key off the HD end and plug it in "upside down". The pile of HDs that caused it to black-screen all work great now.
There has to be a story behind this....