Nintendo VS PCB Issue

Culcuhain

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Ok. I am down to one last Nintendo PCB that is wonky and it is driving me nuts.

Cabinet works good with my other 10 boards.
New set of roms burned and working PPU and CPU pulled from a working board(tested just prior to working on this one)
All voltages are fine.

All I get is a purple screen like the PPU is dead (it isn't. Tested it in several boards)
No audio
No clicking on the coin counter.

Just the purple screen and the normal audio hum....
 
Ok...

I have my proper volts at the connector. (disconnected.)
I hook up a good board. I have the proper volts at the connector and on the pcb.

I hook up the bad board and all the volts are good EXCEPT
the 5v. It is showing 0.17 on the board and on the connector (hooked up)
I checked the volts from backside and the pcb is it is low.

So it looks like there is a short in the 5v on the PCB somewhere. All my other boards (10 or so, I am a hoarder) work just fine.
 
I've had this happen when there was Acid damage on the board. Check near the battery holder, the 2 chips near the battery, and the socket above the battery.

2 other things to check are to do a visual on all the caps. They tend to get bent and 2 legs may be touching. The other thing is the diode on the 5V line. IIRC, there is a diode, a lot of the Nintendo boards have one.
 
This is where an ESR meter comes in handy.

All an ESR meter is... is a high frequency milliohmmeter. Use it to find where the resistance between +5 and ground is the lowest and you'll be right in the area of the short circuit.

RJ
 
Update.
I don't yet have an ESR Meter but I will remedy that quite soon.

Here are the readings from my diodes from the multimeter set on diode.
diode # Low High
D1 N/A N/A
D2 N/A N/A
D3 585 ∞
D4 590 ∞
D5 320 320
D6 583 ∞
D7 320 320
D8 490 ∞
D9 603 ∞
D10 1170 1170
D11 560 1180

D1 and D2 do not exist on this revision of the MB (MDS-05-CPU)
So going off what I see, it looks like diodes
D5, D7,D10, and maybe D11 are toast and the rest are ok...

Anything wrong in my assumptions?
 
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