Mine suddenly went out on me. Was working great, hadn't used it in a while, bought a PowerPak and returned to my console with new-found passion. But the PowerPak wouldn't work... Twice out of ~50 attempts at reseating it booted. I assumed it was the PowerPak as normal games would boot just fine. In the past day or so though it's started taking several re-seatings to get normal games to work, and tonight, nothing. Over half an hour of reseating the cart to no avail, multiple games tried, cleaned both the connector and the carts, still nothing.
Any ideas?
Did you try removing the cartridge slot from the motherboard for cleaning it? In most models of the SNES that piece can be removed for a more thorough cleaning and also re-seating it (or installing it backwards) tends to help with cartridge boot issues.
maybe some physical adjustment is needed? the pins might need to be bent back into shape to make a solid connection with the games
whatever you do, REMEMBER before opening the SNES to disconnect it from the mains and turn it's power switch to ON , as this will discharge the mobo and you won't have to replace the onboard fuse.