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Issue with SA-7800

Back in business. So D33 is on top left. You should have - 0.6V on anode. If you brush that PCB you find parts and traces easily.
 
Ah yes in that last pic there are indeed two diodes - top left and bottom right. Quite right that a little cleaning of the board will make parts identification easier.

I am not commenting any further as enough help is going on - I will just observe :-)
 
Any help is welcomed. In this layout we have negative rail on left and positive rail on right so it is easy to identify all components
 
q35 appears to be not working then . or you mistook it for emitter .. to be sure get its emitter voltage .
just get all 3 and we can work it out from there
 
Ryan Walton said:
well if top left is a diode than you can see my reading were 0.4v and 0v... faulty?
Click to expand...

Not necessarily, it's what is getting TO the diode (or not getting to it) that is the issue.

You can use diode test mode of your MM to test the diode itself. Generally they either work or they don't
 
A diode acts like a gate, only allowing current flow in one direction. If tests good in one direction and not in the other direction it is good. If it tests good both ways it has failed. If it tests bad both ways, it has failed.
 
This is q35... i thought the top middle was the base, but could be wrong? DC voltages on each

q35.jpg
 
I was just about to say solder looks dodgy, as does the neighbouring transistor to the left - mucho reflow on those :-)

I had an SX-880 which would not leave protection and a reflow of a couple of transistor joints fixed it right up.
 
voltages not making much sense but pin 21 should have one of those negative voltages instead of the positive one that is there .
 
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