Im sure its been discussed ten million times but has anyone run into dead cartridges and were able to fix them? I have two games that wont play properly.

Pac-Man 2 (Genesis.) Initially a white screen. Cleaned contacts, eventually could get a garbled screen but i dont think i could play it.

Shinobi 3 (Genesis.) Black screen or white screen. Cleaned the contacts, didnt help.

I opened up Shinobi. All the soldering joints and capacitor look fine. I was thinking maybe the sole capacitor needs to be replaced. I dont have a capacitor tester to see if theres anything wrong with it