Green screen solid light.

wafflecoptergames · Post by **wafflecoptergames** » Wed Apr 24, 2019 4:26 pm

So I bought a system on ebay knowing it was broke. I asked seller for details on symptoms and got no response. After a few days I pulled the trigger and spent the $12. So far all I get is a green screen. I found a bad cap so i changed it and found that the cpu was getting hot to the touch after about 30 seconds. Not warm but so hot i couldnt touch it. I swapped it out for a known good cpu and still the problem persists. Ive replaced the 72 pin and cleaned the whole board. I cant find any obvious problems and cant feel any other chips getting hot. Throughout about 100 resets i got 1 grayish blue screen and 3 graphically buggy screens(only got a picture of 2). Any ideas of where to go next?

Post by **lidnariq** » Wed Apr 24, 2019 4:53 pm

Looks like the PPU is at least somewhat operational, if those single tiles don't change with time. I'd check the CPU's RAM.

wafflecoptergames · Post by **wafflecoptergames** » Wed Apr 24, 2019 5:03 pm

That was the direction I was leaning towards but I dont have much experience with these systems to properly diagnose these more in depth problems. I have a spare board that had a bad ppu so I'll steal the ram off of it and see what that does.

wafflecoptergames · Post by **wafflecoptergames** » Thu Apr 25, 2019 8:58 am

Swapped out the ram and still nothing. I found what looked like a bad trace on the psu and bridged it and still the green screen

Post by **lidnariq** » Fri Apr 26, 2019 7:05 pm

It'd be weird to me if enough of the PPU is working to draw a stable green screen with sprites that look like they're valid CHR contents, but not enough to operate.

Do you have any test equipment? (scope? logic analyzer? voltmeter? frequency meter? flashcart? a resistor and pair of headphones? random components?)

wafflecoptergames · Post by **wafflecoptergames** » Fri Apr 26, 2019 8:47 pm

Only thing I have is a generic multimeter. I noticed somebody else has disabled the lockout chip presumably an attempt to fix the problem. The board is a cpu-10 if that helps.

Post by **lidnariq** » Fri Apr 26, 2019 8:56 pm

At this point, the last thing I could do with just a multimeter is make sure most of the lines in/out of the CPU and PPU are still toggling. (logic tester, if you 'meter has it. Vac otherwise)

nesdevwiki:PPU pinout, nesdevwiki:CPU pinout.

nesdev.org

Green screen solid light.

Green screen solid light.

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Re: Green screen solid light.

Re: Green screen solid light.

Re: Green screen solid light.

Re: Green screen solid light.

Re: Green screen solid light.