Williams Smash TV garbled sound (repair log)

timiskander

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For the archives...

My newly acquired Smash TV started putting out really garbled sound with a lot of cutting out and distortion. I bit of poking around revealed that my +12V supply was at about 3.5V :O

Fixed the power supply (a switcher that had a couple of bad caps and a cold solder joint on the 12V rail choke) and its all loud and clear again!
 
-5V will also play a role in garbled sounds. the digitizer in particular uses this voltage, so everything outside the FM (MIDI) and explosions will probably sound weird. if in doubt, replace your power supply.

if you have a vast collection of Williams/Midway games, Mortal Kombat and NBA Jam came with harnesses to go between the main and sound boards that don't include -5V wiring, as those games didn't need that voltage. or in other words, if your harnesses got mixed up and you're using an MK/NBA Jam one on Smash TV, that will mess up your sounds too.
 
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