NES front-loader, garbled graphics

Hello!

I have read just about every NES thread on here and I'm still stumped. I did the obvious stuff - new 72 pin connector, cleaned all possible contacts, tested games and connector in another system... no dice. Aside from the looking like scrambled ass part, the video signal is perfect and crisp. Audio is 100% perfect, and controller input works as well. I can do fairly basic troubleshooting like continuity and voltage but I'm not sure where I should be testing. What else can I try?

I have a bunch of "harvested" chips from two other NES systems (PPU, GPU, RAM, etc.), but I don't know if any of them are working... could come in handy for trial-and-error assuming they aren't fried.

Just for fun - see if you can identify the games!

http://imgur.com/S1SKz
http://imgur.com/zR3kT
http://imgur.com/LA1vJ

 

You might wanna try replacing the RAM; failing that it looks like a PPU issue.

 

Just a thought, I've often found some games do what you're seeing when you've installed a new 72 pin connector and you've got the game in the locked-down position. I've found that not locking the game down solves the issue, at least until the new connectors is broken in. Also, with NES games being so old, I've found you often have to clean them with a magic eraser to really do the job.

 

He said that he cleaned everything and tested the connector and games on another system so those can't be it.

 

He did, but he didn't specify *how* he cleaned the games and if he's locking the cart down or not

 

I clean my games with q-tips dipped in rubbing alcohol. I think that would work better as long as you applied enough pressure and go back over with a dry q-tip. They say don't use rubbing alcohol but I've never heard of one case when that has done damage and it works well for me.

 

That's normally how I clean mine (isopropyl alcohol specifically), but as I said, I find NES games often need a scrub with magic erasor as well as isopropyl alcohol.

 

Yeah no matter how hard I try I can't get the contacts on some to look perfect. I have to buy a Nes screw driver so I'll be able to do it effectively though as much as I'm into retro gaming I should of had one a long time ago.

 

I tried both the eraser method and used 99% isopropyl alcohol. Like I said, the connector and games are perfect in a different system. Tried different cartridge angles etc.

ApolloBoy - I am not very comfortable at soldering but I'd be willing to try. I'd like to exhaust my other options first before I do that, since there's a good chance I'll wind up killing the board. I have access to a reflow machine but don't know how to use it.

Are there ways I can test the chips first to figure out what's broken before I start pulling things off and making a mess? The RAM is from two different revisions so they're different manufacturers... does that matter or would I have to replace both?

 

I don't know how one would begin to test out each chip unless you went really out of the way and switching chips de-soldered and soldered one onto a system that still works although I don't know much in that department. I'd probably cut my loses and buy a new Nes system.. maybe keep the shell to put onto another one if you like.

 

Got a new system board, but it has @$#% wavy lines. Kind of tempted to transplant the RF box from the original board in my post into the new one.

 

If you want to remove large through holes chips like the NES PPU, Use a heatgun, best and safest method short of having a professional hot air station.

I put the heatgun on its side on a table with the nozzle blowing over the edge of the table.

Hold PCB on one hand, other hand had chip extractor grabbing the PPU. Heat the board from underneath until the chip comes loose. I also take a minute to evenly preheat the board before concentrating on the chip to remove, in order to reduce thermal stress. Dont solder new chip in, use sockets.

I have fixed 2 NES with graphical glitches by replacing PPU.

 

I put in a 40-pin socket where the PPU was so I could try the other ones I had laying around... one seemed "better" but still garbled. Also tried swapping out the 373 chip with no luck. Now I'm not sure if I messed up and could have messed up a contact somewhere. Either way, I'm pretty much still at square one but a bit more confident with pulling/replacing chips

 

There's at least one broken PPU address trace, but nothing that indicates serious damage. Make sure you're checking from PPU to 373, and 373 to cart edge. From the pictures I'd suspect it's A6-A12.

SMB and Kid Icarus?

 

Yup, that's two of the games

This may be an obvious question, but is there a reference of which pins I would check for bad connections between PPU->373 and 373->cart (without going cross-eyed trying to decipher a schematic)?

http://wiki.nesdev.com/w/index.php/PPU_pin_out_and_signal_description
Looking at this, I only see A0-A2 and A8-A13, but not A6-A8. Is it possible these are labeled differently in other references?

 

I once accidentally cut the trace for PPU pin 25 on my famicom, which corresponds to A13 and it resulted in graphic corruption VERY similar to what you are experiencing.

 

AD6-7 is PPU A6-7 once they're latched by the '373, so trace from the PPU to the '373 and then the '373's outputs to the cart edge. A8-12 is directly A8-12. The A0-2 labeled are actually CPU address line inputs, the pinout isn't very clear. You only need to worry about the PPU address line outputs.

A0-3 ("AD0-3") are definitely good because the while the nametable is fetching wrong tiles, they are still complete tiles. A4-5 are probably good too since Mario's sprite is OK, and he's most likely 4 contiguous tiles. A13 is probably good if Mario starts.