Taito Frontline arcade pcb repair #2
Game played but without sound. Diagnosing sound problems on these boards is pretty easy as all of the sound generators have test points on the top board – PSG1-4, DAOUT. Attaching power speakers here lets you hear the individual sound outputs before they are mixed. If they are all silent then there is most likely a sound CPU problem, but for this board everything sounded great at the test points. The sound is then mixed and sent to the two volume controls – powered speakers can also be attached directly to the right-most and center pins of the volume pots to check audio post mix. From there it’s almost straight to the power amp, and if you can hear audio over powered speakers attached to the power amp input (pin 1) then almost certainly the power amp is dead (or is missing +12V). In this case the MB3730 amp was replaced to fix sound.