Namco ninja assault loud audio hum

neopolss

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Donor 6 years: 2013, 2016-2020
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It's a pretty loud hum that only plays when the game is loaded, so when the cab is first turned on, there is no audio hum until the game actually starts running. This is on Naomi hardware, although there is an external amp for the speakers and sub. Anyone got suggestions on what may cause so much feed in the line?
 
Gonna swap sound amps and see if there is any change, then move on to power supply
 
i've had the same problem. never did solve it properly though i swapped the Namco audio amp for a small amplifer from Parts Express and i remember it helping some though i think it still has some hum.

i also noticed that a dedicated one on location had the same issue.

please let me know if you figure out what's going on; love to get it fixed.
 
Ill keep you posted. I also would think the namco mother board ma be an issue too since the output is from rca jacks on the filter board.
 
i did replace my entire main pcb since i picked up a second NA kit up off of KLOV and my old main board had an issue with one of the TEST buttons not working right.

hmm. i wonder if there is a cap issue with the main boards?
 
I put another amp in it to see if there is a change. The hum actually got worse. I'm leaning towards the amp as the problem. My esr shows a bad 16v 1000uf cap and a bad 16v 330uf cap on it. There's also some large poly caps that I have a hunch are probably bad. I may just replace them anyway.
 
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