I have an Amiga 4000 that when I turn it on only get a grey screen. It powers on (lights and all come on), using CTRL A+A restarts it (HDD spins down then on again and Caps locks flashes). I just put in a new A3640 CPU card and the motherboard I got was from Ebay (about year or so ago) with a coin battery replacement for the barrel. The board is pretty clean and traces seem fine. I have stripped it all the way to just chip RAM and 3640 board only and still only get gray screen. Capacitors look good, but I was wondering if anyone had a electronic manual or Doc on testing motherboards (ICUs, Caps, resistors and such) and what the readouts should be on a multimeter. Does anyone have any ideas on what I can check for?I really want to get her up and running (been a few years). Also is there a way to test the PSU and what should the readings be on the pins in the plugin to the MB?