nes suddenly not working

[threedog]

Got a "toaster" NES from Ebay about a week ago. First thing I did was disable the lockout chip. Then I replaced the 72 pin connector with a standard 72 pin card edge connector. Soldered it directly to the board. After those mods, my NES played every single game I tried on in, 100 percent of the time, with no glitches. But it suddenly stopped working. Most games don't boot at all, and those that do boot just give me a scrambled screen, but perfect sound, and the system does not respond to the controller. Is it possible that I messed things up when I disable the lockout chip? I tried to break pin #4 off, but I ended up ripping it clean out of the chip instead. Is it possible that the chip has failed? I made sure the cartridge connector was clean, and checked all the solder joints, too. The only other thing I can possibly think of is that I may have damaged something with a speaker magnet while I was test fitting components in a case I want to try. Is it possible for a magnet to damage any of the chips on the NES motherboard? Sounds unlikely, but I'm all outa ideas. Thanks

P.S., I checked the voltage on pin 36 on the cartridge connector, and it's only putting out around 3 volts. I'm getting a full 5 volts from the main regulator. Is this normal, and if not, could it be causing my problem?

[threedog]

(bump) nobody's fixed or encountered this problem, eh? Oh well. I'll keep plugging away at it until I figure out what's wrong, and if I ever do fix it, I'll be sure to post.

[threedog]

I even tried my NES with a Game Genie. The GG boots up the same way all other games boot up. Scrambled graphics... It seems to give me the same pattern of scrambled graphics with every game I try. I'm starting to suspect my PPU is fried, maybe by static or something? I'd be willing to try replacing the PPU if I can find a replacement. Anyone know where I can score one, or would it be cheaper to replace the entire NES? I'm going to try replacing the lockout chip, since I know I damaged mine slightly when I disabled it, but before I do, could someone please tell me if the lockout chip on the NES motherboard the same as the lockout chip in a NES cartridge? I noticed that the markings on the two chips are different... Thanks

[dsv101]

i have the same problem with my first nes, i accidentally ripped the pin out of the lockout chip, it lights up, nothing gets hot, and it doesn't play games. Then i started wiggling the cart around in the 72 pin connector, i started getting some video (well colors and a few audio bleep bloops, lol)

thats where i stand, it must be the lockout chip

[threedog]

i have the same problem with my first nes, i accidentally ripped the pin out of the lockout chip, it lights up, nothing gets hot, and it doesn't play games. Then i started wiggling the cart around in the 72 pin connector, i started getting some video (well colors and a few audio bleep bloops, lol)

thats where i stand, it must be the lockout chip

Sweet, could be an easy fix then. I -think- the lockout chip on the nes motherboard can be replaced by the lockout "key" chip found inside a game cart. I'll try it later today and let you know how it turns out. Thanks!

[dsv101]

Cool, if it works, ill try it too, i have a zelda two cart that rarely works for more than 1 minute, ill take the chip from there

[threedog]

DSV101, I swiped the lockout "key" chip from my copy of Jaws and installed it in place of the lockout chip on my NES. It didn't fix my problem, but it didn't make it any worse, therefore, it would seem that the chips are interchangeable, so give it a shot, it might do the trick for you. While you have the chip desoldered is a great time to bend pin 4 out of the way without having to hack away at it and possibly damage the chip.

Still baffled by my Nintendo's sudden refusal to perform. About the only thing I can think at this point is that the PPU got static zapped or something. Only way I can think to test this theory is to replace it with a known good PPU, but the only one of those I have handy is the one in my Famicom. I'm guessing the answer to this one is "no", but does anyone know where I can get a PPU for a NES other than from, well, another NES? In other words, there isn't a suitable off-the-shelf component I can use, is there?

[Adr990]

Hey Threedog,

I've got the same problem on 1 of my 2 NES's, and actually tried the same things.
I did replace the Lockout Chip with one from a game, but still got the same problems.

Now I've tried everything, also did some stuff on the PPU (pin 21) and some other things I can't recall.
Nothing worked.

So I came to the conclusion:
It must be something else than the mother board, or the PPU is actually broken.

I've been told that WD40 does wonders, so I'm gonna try that on the connector's of the 72 PIN connector and so.

I'll report back if that worked, but I kinda lost hopes.

Adr990