@ D: I don't have the a530 book. If you would be so nice to post some info, I would bemost grateful.
@Tenacious: I used the schematics for powering the A500 from here:
ianstedman. I used the pinout for the power connector from
here. Maybe that's the problem?
I am using the same PSU for both devices and even tried powering the A530 from the ATX PSU (first) and then the A500 from its original power supply. The A500 alone boots up fine from the ATX PSU, but when the A530 is connected nothing happens and I get no power reading from my voltage meter.
When I bridge jumper cn16 the A530 gets 12V from the A500, because the fan spins up and the HD reads 12V, but no 5V.
And yes, figuring out the voltage meter took some time :-)