Another black screen snes topic.

My quest to have a modded snes has let me to where I am today. I have one 1chip snes not liking being put in 60Hz (already another topic on this site) and a older model one with the two PPU chips (easier for me to mod).

Sadly, the one with the PPU chips need some repairing.

The best output I can get from it is a black screen with perfect sound. if not, it's just a mess of pixels with very worrying sound. I've given it a clean, inside and out. I'm guessing something need to be replaced.

 

Some pics might help. Everything else is just guessing.

 

I took a few "fresh" photos.



I get a different one every time I switch it on. I got more this time round, before, 80% of the time it would've been a black screen with good sound.

 

Don't know if I'm on the right track, but here is a little update. I got a hold of a digital multimeter (a very cheap one).




Anyway. I went to check the big-ass capacitor on the snes. I checked up a guide that said one way to check if a capacitor is good, is to:



Set the meter on Ohm range (Set it at lease 1000Ohm = 1k)
Connect the Meter leads to the Capacitor terminals.
Digital meter will show some numbers for a second. Note the reading
And then immediately it will return to the OL (Open Line). Every attempt of Step 2 will show the same result as was in step 4 and Step 5. It’s mean that Capacitor is in Good Condition.
If there is no Change, then Capacitor is dead.


Well, I tested this on a old graphics card and I got a reading on all its capacitors. I then tested the one on the snes and I got nothing. I removed it from the board and tried it again. Still nothing. Is it safe to assume that this could be the source of the problem?


Here are pictures of the board with the capacitor removed.

 

The plot thickens. I removed all solder off the capacitor and I am now getting a reading. So now I'm back to square one.

 

You don't test capacitors in circuit.

 

I highly doubt it's the cap at fault.

Check the ppu's or the ram.

 

How would one "check"? I've given them a look over and there is nothing I can see that could be out of place. I've put the capacitor back and I still have the same problem.

 

The service procedures for the SNES are unknown to me, however I can offer something.
C59 has leaked onto a trace below it.
Check continuity for all the traces for PPUs and RAM.
Check for stable supply voltages too.

Without a test program and waveforms for comparison there is very little you can do to "check" these PPU and RAM chips.

From what I've seen some people will salvage the PPU and RAM chips from other consoles, but you need a donor. Knowing that these are the more likely chips to go, luck isn't on your side.

 

Yay more fun things to do today.