Super NES with no picture: replacing a failed PPU

Why audio proves the CPU is alive

Audio that plays correctly means the CPU fetched the game code, ran it and is writing commands to the audio subsystem over the same bus the PPUs use. So a black screen with audio is not a bus fault and not a cartridge fault. It is the video generation path.

Distinguish between a black screen and coloured bars. Fixed coloured bars usually mean the PPU is producing sync but no picture data, which points at the PPU itself. A completely black screen with no sync at all can just as easily be the video encoder or the multi-out socket.

Narrowing it to one of two chips

The Super NES has two PPUs that work as a pair: one handles the background layers and one handles sprites and colour. A failure in one often produces a picture that is present but wrong, while a failure in both produces nothing. Use a game with a simple, static first screen so you know exactly what should be on the display.

Check the easy things first. The multi-out socket on an SNS-001 cracks its joints the same way a Mega Drive AV socket does, and the video encoder can fail on its own. Neither is worth a PPU replacement.

1. Confirm the audio works by running a game with a title theme and listening. Audio plus a black screen is the signature of this fault.
2. Flex the AV cable at the multi-out socket while watching the picture. Any change means the socket joints are the problem, not the PPUs.
3. Measure the 5 V rail at the PPU supply pins. Both PPUs run from 5 V and a low rail will blank the display entirely.
4. Check the video encoder output at its pin with a scope. A composite signal present here but absent at the multi-out means the socket or the cable.
5. Check the crystal oscillator. A dead clock stops both PPUs and produces a black screen with working audio, which is the exact symptom you are chasing.

Replacing a PPU without lifting the board

The PPUs are 100-pin quad flat packs on 0.65 mm pitch, soldered to the top of the board with no access from below. Removing one requires hot air or a rework station, a preheater, and a lot of flux. Practise on a scrap board first if you have never done a 100-pin QFP.

This is the point where many repairs end badly. If the diagnosis has not positively identified a specific PPU, do not remove anything. A board with both PPUs intact but a bad encoder is a twenty-minute fix; a board with a lifted pad under a PPU is scrap.

1. Replace the crystal oscillator first if the clock is dead. It costs almost nothing and it explains the whole symptom.
2. Reflow the multi-out socket joints and re-test before touching the PPUs.
3. If a specific PPU is confirmed dead: preheat the board to 120 °C from below.
4. Flood the PPU pins with flux and remove the chip with hot air at 350 °C, moving the nozzle in a slow circle and lifting only when every pin is molten.
5. Clean the pads with braid, align the replacement by two opposite corners, and tack them down.
6. Solder the remaining pins with a drag technique and check for bridges at 10x before applying power.
7. Test with a game, then run for thirty minutes and re-check the joints for any that have moved.