(ET) More info

[Chris Zach <czach computer org>]

I seem to have been mistaken; the top sensor is marked as 54. So that's 
correct. Also the output to FU3 and the attachment plug are on the 
correct side of the shunt.

Disconnected the control fuse, no fault. Connected light fuse, no fault. 
Connected control fuse, fault. Disconnected both of the 22 connections 
off the control fuse, no fault. Connected either, fault.

Disconnected card4 completely: No fault. Ok, so wherever the fault is 
it's coming through something in card4. Something big, no question. Next 
step is to check each pin going into the card4 edge connector. One of 
those has to have gone to ground.

Then it's simply follow, isolate, fix.

Getting closer.

Chris