Is your NES not working? Are your games acting glitchy? Controllers behaving strangely? This is the place to get help!

Link to previous thread

First steps to take:

Games don't play correctly:

1. PRESS DOWN on the Game Pak until it locks into place
2. Clean games
   1. Disassemble cartridge (might need special tools, check amazon or ebay)
   2. Gently use rubber eraser with no grit on edge pins
   3. Use window cleaner or isopropyl alcohol with lint free cloth
   4. Spray contact cleaner on the pins
   5. NEVER EVER BLOW IN IT
3. Clean NES connector
   1. Ancient cleaning kit
   2. Spray contact cleaner on the pins
   3. Boil it
   4. Bend pins (risky)
   5. Replace the connector
4. Already tried all steps for cleaning game & cleaning NES above?
   1. Try a Game Genie, the thicker PCB might make better contact with the NES and the tighter connector might make better contact with the cartridge
   2. Try another game cartridge
   3. Try another NES
   4. Try r/consolerepair
   5. NES Schematics

Power Supply:

1. For the NES any power supply that can provide 850mA (or higher) at 9V and has the right shape connector will work. The original NES uses an AC adapter but a DC adapter will work too.
2. For the Famicom you must use a DC power supply with center negative that can provide 850mA (or higher) at 9V-10V. Do not use a NES AC power supply on a Famicom!

Controller buttons don't work or think a different button was pressed:

1. Take them apart and clean the contacts on the PCB, not the rubber membrane

Display problems:

1. Use a CRT monitor or TV
2. Don't use an LCD or LED TV - many LCD or LED TVs do not understand the 240p video signal that the NES puts out
3. If you must use an LCD or LED TV, get an upscaler
4. Use the composite RCA/AV connectors on the side, don't use the RF/antenna/aerial
5. If you must use RF, don't use the RF/antenna/aerial switch box, use a small adapter instead, be aware though that modern TVs may not work with the analog RF signal and only with ATSC or DVB digital signals
6. Wavy lines: replace the capacitors in the NES

Hardware Failure Diagnosis:

1. Power rails first: Multimeter check - verify +5V at 7805 regulator output and at PPU/CPU pins. If low/absent, check caps and regulator.
2. Composite video signal: Scope the composite output (RCA jack center pin or PPU pin 21). Should see ~1Vp-p composite video signal with sync pulses and color burst. No signal = dead PPU or supporting circuitry.
3. Audio output: Scope audio output pin (RCA jack or APU output). Should see audio waveform when game is running. No signal = APU problem or output circuit.
4. If power is good but no video/audio: Most likely failed capacitors in video/audio output path, or dead PPU/APU chips. Check/replace electrolytic caps first (cheapest fix).
5. If video signal present at PPU but not at RCA jack: Problem in video buffer/output circuit between PPU and connector.

Before asking for help, make sure you have followed the steps above.