SNES graphics layer repeating in bands. Help!! please.

[tommyg]

right, i got this snes with messed up graphics - pics attachached-




i hope that i just have to clean something inside it, but i can't see anything that's obviously bad, and wonder if anyone knows where i should be looking!
cheers!!!!

[l_oliveira]

Ｔｈａｔ ｓｅｅｍｓ ｌｉｋｅ the video ＤＭＡ (Direct Memory Access) circuitry failed or the VRAM addressing for one of the PPU chips (yes there's two PPU chips) failed.

Since the background looks fine I bet the VRAM is alright.

If you dismantle the console to take a look, be sure to inspect the traces for corrosion (and hope you find one because if the traces are fine, the problem  will be on one of the chips.)

[tommyg]

hi! thanks for the reply! i already opened it to have a look, and what i found were a lot of small sticky treacle like blobs all over inside it! is this normal when opening an old console???

i thought that some of these may have been bridging some points that weren't meant to be, so i cleaned off all that i can see (and i looked pretty hard), but the console still works in exactly the same way! i can't see any more damage/dirt/wrongness inside it on the main board (it's the kind with integrated spc).

could this problem be caused at the cartridge slot, do you know? if pins were bridged that shouldn't be?

i even tried bridging pins myself on the ppus and various other chips, just for a bit of a laugh to see what would happen - some crazy pallette stuff, graphical corruption and mosaic (i think it's called!) effects going on when i did this!!! and the console is no more broken than it was before! crazy!