Hey guys, so I've been repairing consoles to convert them to RGB and I happened upon a particularly disgusting system for eight dollars.
This thing had tons of (probably 30 year old) dead bed bugs and insect droppings inside, was rusted out on the RF box and shield, didn't power up at all etc...
I cleaned the shit out of the shell replaced the caps (which were ALL totally bursted) and promptly redid the RF section. No dice, no power even though the regulator was seeing 5V if I shorted pins 1 and 2... Then I realized that the LED pad had come up and and needed to be manually wired over its trace.... Then I realized that even though I got the LED to light up again while RF pins 1 and 2 were shorted, the power switch wasn't working and needed to be totally cleaned out (emery board on the contacts)... Then I was getting a "pop" while turning the power on from the audio jack, but no video. Then I figured out the trace had broke from the 330 pf ground cap to the video pin (I have NO idea how this got cut).
So after all that and cutting the lockout chip I have ended up with a white screen and a pop upon turning on the system. I did the following... swapped out 72 pin for one I know works, filed down corrosion off of the motherboard side of the 72 pin, and scrubbed thoroughly with isopropyl alcohol til all the black had left. I swapped out the rf section with a USB clean power and simple video amp one I made a while back. I noticed the green trimmer had a shitload of rust in it and returned a "2 pf" reading on my meter so i replaced that with 2 15 pf ceramics in parallel.
Just for shits, I reconnected the lockout chip and it seemed to approve of my cartridge connection. I reheated many solder joints in tribute, but the solder gods did not yield a plentiful harvest.
So here's my theory. All the caps were popped... even ones that were underneath the shield which seemed to be untouched by the water damage. That leads me to believe that maybe something bad happened as far as power was concerned for this thing. I'm thinking maybe someone plugged in a tip positive supply after one of the electrolytics had died open which caused 13 volts over the wrong side of all of the other electrolytics. Must've been some fun smoke. Then once it broke they didn't give a shit about the system and left it in their garage or flooded basement or something. Somewhere where bed bugs wouldn't mind living.
Anyway, I noticed some extremely faded IC's on this guy. Two of the 74 series thingies have very dark and faded text and both of the RAM chips in front of the CPU and PPU are very faded as well. I'm thinking that those may have gotten hit sorta hard during this thing's capacitor apocalypse. The CPU and PPU themselves have a few legs with a tiny tiny bit of corrosion on them but otherwise look totally fine and aren't like heating up or anything. Actually nothing is heating up and everything is getting the proper 5 volts as well.
I'm not awful with analog electronics but I don't know shit about digital. Usually I just use one of those arduino powered "IC Testers" where you pop the chip in and it tells you whether or not it works so you can pop it back in the socket. Unfortunately, the NES is not socketed.
Does anyone know a way I can test these chips without doing the awful job of desoldering? I got a scope an oscillator and a fluke 87. Anyone thinking of anything obvious that I might be totally missing?
Thanks!
-Dave
This thing had tons of (probably 30 year old) dead bed bugs and insect droppings inside, was rusted out on the RF box and shield, didn't power up at all etc...
I cleaned the shit out of the shell replaced the caps (which were ALL totally bursted) and promptly redid the RF section. No dice, no power even though the regulator was seeing 5V if I shorted pins 1 and 2... Then I realized that the LED pad had come up and and needed to be manually wired over its trace.... Then I realized that even though I got the LED to light up again while RF pins 1 and 2 were shorted, the power switch wasn't working and needed to be totally cleaned out (emery board on the contacts)... Then I was getting a "pop" while turning the power on from the audio jack, but no video. Then I figured out the trace had broke from the 330 pf ground cap to the video pin (I have NO idea how this got cut).
So after all that and cutting the lockout chip I have ended up with a white screen and a pop upon turning on the system. I did the following... swapped out 72 pin for one I know works, filed down corrosion off of the motherboard side of the 72 pin, and scrubbed thoroughly with isopropyl alcohol til all the black had left. I swapped out the rf section with a USB clean power and simple video amp one I made a while back. I noticed the green trimmer had a shitload of rust in it and returned a "2 pf" reading on my meter so i replaced that with 2 15 pf ceramics in parallel.
Just for shits, I reconnected the lockout chip and it seemed to approve of my cartridge connection. I reheated many solder joints in tribute, but the solder gods did not yield a plentiful harvest.
So here's my theory. All the caps were popped... even ones that were underneath the shield which seemed to be untouched by the water damage. That leads me to believe that maybe something bad happened as far as power was concerned for this thing. I'm thinking maybe someone plugged in a tip positive supply after one of the electrolytics had died open which caused 13 volts over the wrong side of all of the other electrolytics. Must've been some fun smoke. Then once it broke they didn't give a shit about the system and left it in their garage or flooded basement or something. Somewhere where bed bugs wouldn't mind living.
Anyway, I noticed some extremely faded IC's on this guy. Two of the 74 series thingies have very dark and faded text and both of the RAM chips in front of the CPU and PPU are very faded as well. I'm thinking that those may have gotten hit sorta hard during this thing's capacitor apocalypse. The CPU and PPU themselves have a few legs with a tiny tiny bit of corrosion on them but otherwise look totally fine and aren't like heating up or anything. Actually nothing is heating up and everything is getting the proper 5 volts as well.
I'm not awful with analog electronics but I don't know shit about digital. Usually I just use one of those arduino powered "IC Testers" where you pop the chip in and it tells you whether or not it works so you can pop it back in the socket. Unfortunately, the NES is not socketed.
Does anyone know a way I can test these chips without doing the awful job of desoldering? I got a scope an oscillator and a fluke 87. Anyone thinking of anything obvious that I might be totally missing?
Thanks!
-Dave