Viper Phase 1 / Seibu SPI arcade pcb repair
Sound would go quiet after a few minutes, and it seemed like different elements of the sound would have incorrect volumes (drum track, music, explosions). I think that’s because the sound chip outputs multiple channels which are mixed externally before the stereo amp but didn’t look too much into it.
Instead, I just swapped out all the capacitors in the audio section – I think all are 100uF, 25V. This seemed to fix all the audio problems.