I recently picked up an HP 9815s ( was originally an 'a' model but was upgraded with an 's' cpu board and the option 002 i/o long before me), that displays the "---------------" when turned on. I've scrounged through Google and learned that this particular display is generated by the display board when it has nothing else better to do to direct its attention. After checking that the power supply was putting out the recommended voltages and chasing the +5v around the cpu board and puzzling that for a bit, I've checked for activity at the cpu and found no voltage at all being applied at Vcc the cpu. I've been studying Tony Duell's schematic for the 9815(thank you Mr. Duell), but have not found a reason why this voltage might not be present. Is Vcc switched somewhere? I done some meager sleuthing of the traces around the 6800 and think I chased Vcc to a transistor close by, but need to investigate further this weekend. Anyone chased this type of failure on the 9815 or traced out wether this Vcc is applied at power on or switched by some logic at the power supply board?
Puzzled, but determined, Tom
