Qaudra 840av - help needed, no chime, no video

[AlpineRaven]

Good morning all, 
I received Quadra 840av, did not power up and the PSU has been recapped and is working/how it should be (even tested with 8100 PSU).

I've recapped the logic board - all 15caps (13big/ 2 small caps)

It has been washed through fully with ISO, SafeWash 2000 3 times leaving the board spotless. Logic board does have cap rot - but circuitry seems to be ok.

I've plugged it in, pressed power on button (both keyboard & on the logic board) it shows power LED, fan starts up/PSU indicates working, but no video output and nor sound "Bong".

Where else should I start looking on the logic board to fault find?
Cheers

AP

 

[Byrd]

I’d get it under a magnifying glass and examine traces/corrosion around the more bigger, complex ICs. Use a soft toothbrush dipped in isopropyl alcohol to clean around any damage found, even if it looks slight. Some INOX sprayed around the corrosion would also clean it up some more, and under the ICs.

 

[AlpineRaven]

All sorted - working well
Cheers

AP

 

[Zippy Zapp]

Cool.  What ended up being the solution?

 

[AlpineRaven]

Cool.  What ended up being the solution?

I am not sure, when I couldn't get it booted and nor chime etc...

I was exhausted at that time and I thought I'd try again in couple of days later, but this time it was bench test with Power Supply connected to it (before that the PSU was still in the case), and pulled to minimal spec ram and VRAM was put in, and it fired up with video showing up - I must've done something not right or there could be a tiny amount of water somewhere which had dried up when I tested it again. But prior to testing it was dried up with an heater and left it on the bench vertical for 24 hours.

But the main thing, its working 100%. I am just waiting for a new fan for the power supply to arrive as its very noisy - the more I use it becomes noisier and when its fitted I will get the nubus scsi cards to work.

Cheers

AP