Thanks for confirming and the updates on your progress. From your other replies you've clearly got much more electronics knowledge than me, so just a few more questions for clarification, to try and help diagnosis.
At the end of your original post you wrote this happens even with the floppy unplugged, so is the Panasonic drive your floppy drive or your hard drive?
You wrote that you tried without accelerator, have you also tested with just floppy drive and no hard drive, no accelerator?
What are the ratings of the power supplies you've used? Are they all official Amiga PSUs or do you have something more powerful? (I was recently given 5 PSUs and the specified outputs vary, even for units with the same part number.)
