SNES graphical glitching: need help fixing

[toredauei]

today I found a snes at a thrift store for 15 dollars and, like everything else I ever buy from thrift stores, the price was too good to be true. the system turns on and everything seems to function correctly other than the fact that the picture the system outputs is all glitchy :/ Nothing wrong with the sound or anything, just the picture. Cleaning the contacts proved futile so I opened the SNES up and took a look inside. The only thing I could find that seemed out of place was one of the smaller chips in the top right corner had some corrosion on its legs which I cleaned off. No improvement. If im not mistaken that particular chip isnt one of the graphical chips anyway ( the two that are on top of one another directly to the smaller chip's left are)
Anyway, Ive provided pictures of what the glitched out snes looks like along with what the screen should look like and have also provided pics of the pcb. If anyone can give some insight as to what my problem may be and how to fix it that would be awesome :)
The main PCB

The chip that had some corrosion on it

Konami screen glitched

Konami screen normal

Contra opening glitched

Contra opening normal

[Cyantist]

thorough cleaning off the cartridge port. (credit card and thin wet duster trick) also use a small (i mean tiny like the kind you use for the screws on glasses)) to bend all the cartirdge slot connectors pack up and into place

[Calpis]

It's not the cartridge port, there's likely a damaged trace (specifically data line(s)) between the PPU and VRAM (U4 and U5).

[toredauei]

The thing is, there dont seem to be any damaged traces anywhere. The trace between u4 and u5 seems especially good :/

[Calpis]

It could also be a bad solder joint. You'll have to do more than look ;)

[marshallh]

I bought several SNES that did that, cleaned out the connector and they worked fine. One of them was caked with crap inside but it still worked fine.

[Oldgamingfart]

Try leaving it running for a few hours, sometimes the capacitors need to 'charge up' a little if it hasn't been used in a while.
If it works after that then the capacitors will need to be replaced anyway for long-term reliability.

[toredauei]

which cap would be the one that would need replacing? the gigantic one underneath the shield in the top left?

[Calpis]

A couple of hours to charge a capacitor would require both a very large capacitor and a very large resistor which doesn't make any sense for the SNES. They are used only for AC coupling and decoupling and wouldn't cause this issue. You probably wouldn't even notice a bad capacitor unless it was used to couple video because the decoupling capacitors give eachother redundancy and are only there as a safeguard anyway.

Also, since Contra is 8M, it's unlikely code isn't running from the most significant say 4M of the game. If the game runs (and others do), only with bad graphics, it's a PPU issue, not connector.