Professional software development, amateur BMW tinkering, old arcade game stuff


Nintendo Mario Bros arcade pcb repair #1

Board appeared to play blind – sounds were produced, but no video.  Logic probe quickly revealed there was no video sync signal coming from the video board.

The sync signal is mostly produced by a couple of LS123 chips – there was no output from them – but also no input to them either.  I followed the path upstream until getting to the clock circuit, so much like the Popeye repair the video clock circuit didn’t seem to be active.


In this case the crystal oscillator and LS04 tested fine – the problem chip was the upstream S74 which had failed.  When replaced the board was 100%.






Nintendo Popeye arcade pcb repair

Game did not boot, and seemingly no logic activity anywhere on the board.  The clock circuit is the first place to start for this kind of thing.  It mostly consists of a crystal oscillator, a few resistors/capacitors and a 74S04 in a kind of feedback loop.


I removed the S04 chip from the board but it tested ok – the actual problem was the crystal oscillator itself had failed.  20.160MHz is kind of an unusual value for arcade games, but a replacement was found and fitted and everything worked 100%.