Variation on A4000 dark gray screen problem

[mechy]

I have an A4000 with a very clean motherboard, but it has a dark gray screen boot problem.  I disconnected everything.  Once the insert disk screen came up for about 10 seconds, but then it reverted to the dark gray screen.

I noticed that the PSU fan speed was all over the place, so I thought it might be the PSU.  I replaced it with a known working one.  I powered up and all seemed perfect for 30 seconds, but then the damn dark gray screen popped up again.  Since then, I have been unable to get it to work again at all.  I tried a different CPU card, but that didn't help.  All the chips/memory are secure.

Has anyone experienced anything like this before?  It seems to be so close to working.  I'm stumped.

It smacks of a ram problem, maybe tarnished sockets. Be sure the chip simm is in the right socket and is indeed a chip simm.

Look the Pins in the psu plug over well, if 1 is tarnished or spread open a bit it may be a bad connection problem, usually on the +5v wire.

Reseat the A3640 accelerator board and make sure its on the plastic standoff pins.

Have the caps leaked on the A3640? they are known to eat a trace under the leaking caps at times.

check all jumper blocks. move them on the pins and be sure they are making contact.

Mech

[mechy]

I highly doubt that I have any jumper settings wrong, given that the machine did work very briefly the other day.  Even if I remove all the fast ram, it does not boot with the chip ram.  The daughter board was taken out and had no apparent effect.

Anyone else have any ideas as to how this machine was not working, then working very briefly, now not working no matter what I try?  

I can throw my A3000 against the wall and it will still boot.  These A4000 machines are very finicky?

If anything A4000's are inhearantly more reliable than 3000's due to surface mounting.

The psu's are pretty good. The 3000 suffers from 20 year old sockets that tarnish and make bad contact. Thats being said i have had good success making either run reliable.

Its much like a used car, sometimes used computers have been treated badly or developed problems. Used is used

have you physically pulled the roms and reinstalled them, i have seen roms with a pin bent under that makes contact at times.

i still think you have a trace thats eaten under the A3640 or a contact problem on ram or cpu slot.


mech