Greetings! Been lurking for a bit on these forums, finally decided to register!
A while back I acquired a toaster that was producing some minor graphical artifacts; not scrambled graphics but rather some glitchy graphics (Unfortunately I don't have any pictures of what it looked like, but I can take some shots of it when I get the chance) After troubleshooting it a bit I figured that the PPU or SRAM was likely the source of the problem.
I found a UMC UA6538 on AliExpress which I proceeded to buy as a replacement PPU. I desoldered the original chip and soldered in a used 40 pin socket that was lying around. Everything fit together, but when testing the 6538 with an SMB cart I got some interesting results. To begin, the picture appears to be a very flickery monochrome mess, where absolutely nothing can be made out. (I will post pictures soon.) It looks like something is wrong with the sync as well, the picture is wavy and jumps all over the place. When testing a cartridge, oddly enough, the music and sounds are noticeably slowed down. Not in pitch, but only in tempo. Everything else seems slower as well, things like Mario's jumps.
My guess is that this is a clone PPU possibly made for PAL consoles? I'm not sure but that might explain the slower timing and picture issues. I was also able to test the original PPU in the socket, which still produced scrambled graphics. (They've gotten much worse, I'm assuming that desoldering it may have caused some damage to the PPU.) However, the sound is normal and the picture is displaying fine.
I'm wondering if anyone can help me diagnose the issue here. I will post pictures ASAP. Thank you!
A while back I acquired a toaster that was producing some minor graphical artifacts; not scrambled graphics but rather some glitchy graphics (Unfortunately I don't have any pictures of what it looked like, but I can take some shots of it when I get the chance) After troubleshooting it a bit I figured that the PPU or SRAM was likely the source of the problem.
I found a UMC UA6538 on AliExpress which I proceeded to buy as a replacement PPU. I desoldered the original chip and soldered in a used 40 pin socket that was lying around. Everything fit together, but when testing the 6538 with an SMB cart I got some interesting results. To begin, the picture appears to be a very flickery monochrome mess, where absolutely nothing can be made out. (I will post pictures soon.) It looks like something is wrong with the sync as well, the picture is wavy and jumps all over the place. When testing a cartridge, oddly enough, the music and sounds are noticeably slowed down. Not in pitch, but only in tempo. Everything else seems slower as well, things like Mario's jumps.
My guess is that this is a clone PPU possibly made for PAL consoles? I'm not sure but that might explain the slower timing and picture issues. I was also able to test the original PPU in the socket, which still produced scrambled graphics. (They've gotten much worse, I'm assuming that desoldering it may have caused some damage to the PPU.) However, the sound is normal and the picture is displaying fine.
I'm wondering if anyone can help me diagnose the issue here. I will post pictures ASAP. Thank you!