Thanks! I went through the FAQ as carefully as I could. One more time after reading your post. By now I have repeatedly booted the empeg from the end connector of the IDE cable with the secondary drive, but never with the old primary drive. I can hear it clicking in the drive but it doesn't spin up. If I simply replace the drive, the secondary drive spins up just fine at the same location. I think that is fairly unambiguous and neither a cable or connector can be responsible for repeatedly one drive spinning up, while the other fails.
Or is there something in this logic I missed?