'All' meaning the +/- 8V rails and the +5V rail I assume. It could be a fault on just about any part of the drive. For example, the R/W module will cause a fault if it detects a current in the head (i.e. the drive is writing) without write_gate being asserted. Stop swapping boards! That's no way to fix a computer (any computer, but particularly a classic one). Do you have the printset (schemciatics)? If so, look at the fault logic on the drive select board. You'll see it's basically a logical OR gate that combines about a dozen signals. First check that the output of that gate is asserted (just in case the fault lamp driver has shorted or something, although as you swapped ou the logic board this is unlikely!), then see which of the inputs is asserted. Trace back from there to find out _why_. At least the RL02 can be worked on without extended boards... -tony