SNES: Audio, but no picture

I've acquired a non-working SNES, I've got it all cleaned up, but it's not quite working properly. I get audio on it, but no picture (despite my TV popping up a message selling me the source's resolution when I switch it on). There's nothing wrong with the cable or setup, since it works normally if I swap out for my personal SNES. Any suggestions? I've cleaned the cart slot (as well the board's contacts that the slot connects to) and I've cleaned the AV port too.

 

Do you have the mean to test with a different type of connection? ( I.E. I have both Composite and S-video SNES cables )
Then I would try to trace back the connection as far as possible with a multimeter.

 

I'm using a SCART cable, but I'll see if composite makes any difference.

 

I had such an SNES myself this summer. In the end, some of the capacitors on the mobo were blown. I changed all the capacitors, but couldn't fix it anymore. Don't spend too much time on this.

Check the capacitors under the big cooling metal inside. If they have leaked and done massive damage to the tracks, it is most probably not fixable.

Or: you have a PAL SNES and use a NTSC Scart cable.

 

Try using an RF cable and tuning the TV in. If you have a stable picture over RF then have another look at the Multi-Out port and its soldering (assuming your existing A/V or SCART cables are OK).

If all you can get is a blank screen (with audio) via RF, then it might be a capacitor issue. Try 'reforming' the capacitors by leaving the console running for several hours (turn the TV off). Often something that hasn't seen power for a number of years will sometimes need a bit of 'waking up'.

 

I found with my SNES that it would not produce a video signal with an RGB SCART cable I had - turns out it's not compatible with my cable.

Try it using composite or RF first before cracking the console open, because it might be your lead that's at fault.

 

Okay, I've tried using a composite cable, same problem as before. However, I notice there was a little bit of the picture coming though, I could make out a faint silhouette of the opening cutscene in Super Ghouls and Ghosts. Does this help?

 

Repair SNES motherboard is very hard. They are very heat sensitive. (From what i have experienced) Common failures are:
Black screen - Never figured that out. (Yes i cleaned the games and connector still nothing)
Garbled graphics - Some claim it is the S-WRAM.
No power - Fuse

Never experienced:

Bad 7805.
Bad power switch.
Bad reset button.

Wierd failures:
Mode 7 garbled graphics

At Least the NES you could socket the IC´s, but the Snes..... Is there even a IC socket for the chips?

 

I've had a closer look at the SNES' mainboard, the only thing that really stood out to me were some of the traces look... "funny" in spots. Here's a photo:


The traces still appear to be OK according to my multimeter, so I don't think they're the cause of it issue.

I decided to test the connectivity of that big-ass capacitor. No response. I tested the big-ass capacitor of a SNES board that I know works. There's connectivity this time! So the big-ass capacitor is dead then? Would this be a suitable replacement? It's 2200uF and 25V, just like what's written on the capacitor in the SNES. Speaking of that big-ass capacitor, I notice that there's 2 solder points for it on one board, but three on the other! The dead SNES has 2 solder points, so the capacitor with 2 legs I linked to should be suitable right?

 

That large cap is a filter cap and can cause problems if it goes bad. The value isn't very critical but generally you want to keep to the same microfarad rating and the same voltage or higher. Those caps you linked to will work fine but I would much rather go with a good brand (think Nichicon, Elna or Nippon Chemi-Con) as opposed to cheapo Chinese stuff off eBay.

 

Problem is, that brand was the only one I was able to find that had the correct values. Do you have any suggestions?

 

There's plenty more if you look, including some good brands:

http://tinyurl.com/at5yu6c
http://tinyurl.com/akvyqzj
http://tinyurl.com/alj6qet

 

Man, I was only getting 1 match for "25V 2200uF", why were you able to get more? :\

Anyway, do you think that the filter capacitor is the cause of my issues? Would it be worth a shot to replace it?

 

You can get some problems if the filter cap goes bad. Considering it's such a cheap part I'd give it a try.

 

Fireaza, your problem is not BAD FILTER cap.

You see the rust close to the RF modulator ? it could have traces damaged at the other side of the board (which is covered with black lacquer) and that's probably why there's no video.

Also, you cannot test capacitors correctly with a ohm meter.

 

Ah, good point, I'll check that! Now that you mention it, some of the lacquer flaked off around the RF unit, so something amiss happened there.

 

The damage that unit has, kind of look like water induced damage. Could it be a survivor from some kind of flooding ?

 

guys, this is the exact looking damage my board has which has no video or audio. I'm also in Australia, this kind of damage happens from a SNES sitting in 40c heat in a garage

What kind of voltage should I be getting across those caps marked "10 50s 29A"? Should it be the same across them all or not? cause the two on the left are 12V and the ones on the right are much lower volts.

 

I'm not sure, but here's a photo of the other side:


The brown crap appears to be leftover flux to be, since it looks the same as the stuff surrounding other solder points (like the AC adapter in the top right)

 

Well the only chance you have of fixing it is tracing the video circuit from the output until the video encoder chip.