SNES: b button not working.

When I was given an inoperable SNES, I figured I'd try to save it. Everything looked alright, except the DC power jack was completely gone and the console had no accessories, including AV and power cables. Not a big deal; I found a website where I could order a power jack and acquired all the necessary cords and cables and controllers. Watched a YouTube video to assist with the jack replacement, and after I was done I plugged her in and I was ecstatic to see my games work! Absolutely no video or audio issues. (I should also mention that I did clean up while I had the console open.) Then I tried to PLAY my games.
Every single button does exactly what it's supposed to...except for the 'b' button. The 'b' button does nothing. I had bought two brand new third party controllers, and both had the same issue, so I figured that the controller port was bad. Ordered one and replaced it...to no avail.
I thought, then, that the problem might lie in the controllers. I was at a used game store the other day and they had original SNES controllers for sale for a decent price, so I picked a couple of them up, and even tested them on the working consoles they keep in the store to make sure that the controllers could not be at fault if the problem persisted.
Well, the problem persisted.
If anyone has any idea what the problem may be, I welcome your intellect, guesses and advice.

 

Have you got a other console to try the controllers or a friend's console you can try the controllers?
or even tryed a offical controller pad?

 

It's fairly safe to say the problem is in the SNES. There are schematics of the console on this site somewhere. Find out which controller line might be bad with it on the PCB. There's also a chance that the CPU is bad. Controller inputs are wired to the CPU via some passives.

 

ive seen a Luke Morse video on Youtube where the Resistor on the Controller Port was bad giving symptoms like yours. Also the solder on the Ports is really old so maybe a reflow is needed , check for continuity on the Ports PCB as well


best of luck

 

Thank you guys for your help. I saw the schematic when I was on here yesterday; I should have saved it then. I'll find it again though I will check the solders and try to trace the issue down with the help of the schematics. I'm afraid it might be the CPU that's gone bad, but it can't hurt to check the rest. Thanks!