Hello Glen,
??? Thanks for your suggestions. I google around since a while to try fixing this scope, and checked every element known to interfere with initialization. I replaced the battery by two AA alkaline as you did, and check carefully all the voltages and currents of the supply, which was in any case faulty. I even replaced it by another working one, but no issue.?
??? I am now convinced that it's a matter of an actuator some where, which is checked at boot, and does not return the right value, since the program is looping around a sequence which tests the input relays. The screen is not black, but scrambled, except if I press the blue key at start, then entering the sequence to activate the floppy for PROM update.
??? To fix this scope might be possible with the firmware source program (68020), but reverse engeneering of such a 8k piece of firm is out of my skill, even with a sophisticated logic analyzer (which I don't possess anayway). That's the reason for which I was asking Bill E if he was selling a motherboard.
???? Jean-claude
JCB_SFR