Black screen with NTSC SNES

I've been fixing SNES consoles for awhile now, but I've just now come across an issue I've never seen before. I've fixed up an NTSC SNES, but when I go to test it, I get a black screen. There's nothing wrong with the power, I get the red light, and I'm using the same AC adapter that I do for my personal SNES. There's also nothing wrong with the video cable or TV, because, again, I'm using the same connections as my normal SNES.

What is interesting, is when I switch the console on, my TV pops up the resolution of the SNES. It looks like something is going though, but it's not the picture or sound from the console. I've given the cart slot and the part on the motherboard that the cart slot slots into a good clean. I've tried changing mainboards and cart slots, same issue. Any ideas guys?

 

NTSC SNES requires DC input. If you used an AC adapter, expect something to be fried in every NTSC mainboard attempted.

 

I'm using an official Nintendo NTSC SNES power brick, so it's not that Like I said, it's the same one I use in my personal NTSC SNES, and it works fine.

I think I've narrowed it down to the connector. I was able to get the console to work with one connector, but not with a different one. This is kinda weird to me, since the connectors are so simple, they're just a bunch of contacts. About the only thing that should go wrong is they get dirty, and I've cleaned the hell out of them.

 

Not weird at all. They can get dirty, corroded, dry joints, snapped pins... all sorts. What you clean them with could have an adverse effect, too.

If it's definitely the contacts and you can't fix it, then replace the edge connector.

 

Or maybe not. I tried using the connector that was working with a different mainboard, and I'm getting the black screen again :\

 

I hate to say it, how are the capacitors? Seen a few of these now with dried up caps (not as bad as some sega's though).

 

I had a look at the big one near the connectors, but there didn't appear to be anything wrong with it...

 

Doesn't mean anything.

 

Yea that big one, if it is the one I am thinking is pretty stout. It's those bloody smd (small usually silver ones) ones that are the problem.

 

Well, I tried testing the resistance of that big-ass capacitor. Now, I may not know much about electronics, but I should be able to get a current to flow from one leg of the capacitor to the other correct? I wasn't able to get a single measurement off the thing, I might as well have been sticking to probes into the air. Is the capacitor dead?

 

Normally you'd have to use an (expensive) ESR meter to test a cap that's in-circuit. An in-circuit resistance test (with a standard multimeter) will throw up a false reading because of everything else in the circuit.

You can use your multimeter as an ohmmeter to test the capacitor, but only out of circuit (using the high ranges 10K-1M). It will tell you if it's shorted (zero ohms) or if it's completely open (no reading). Of course with electrolytic's you have to observe the correct polarity as well.

Watch the meter, as normally it will go to zero then move slowly towards infinity. This is normal for a 'good' capacitor as the cap is being slowly charged up by the multimeter's battery. This won't however, tell you if the cap is within tolerance. It could still turn out to be faulty!

If in doubt just replace it with a standard electrolytic. It's not like they cost a great deal.