Galaga has no sound

C65Mustang

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I have a Galaga that I have been working on and finally got the monitor up and working but there isn't any sound. This is how it was when I got it. I have installed and checked a new switching power supply and both 12V and 5V looks good when I just have the AC power wires connected to it. When I power on the whole cab the 12V jumps to 15.8ish area and this is how it was on the old PS and the new one as well. This is measured at the J2 power connector on the PCB. I don't know why the voltage change under load. Also I have several socketed chips on here that have corrosion on them and I have started cleaning the leads but some are very fragile. What should I check next or try next?? I will provide pictures of the corrosion issue on the board in another post.
 
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You also have the flat resistor packs. I would suggest a renew kit for reliability. Your current problem is probably a bad audio amp or tantilum cap. In audio section.

See if C23 is the problem, if the amplifier is good.
 
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Recap the audio section.

Are you hearing any noise at all from the speaker? You may have dirty connections on the sound PROMs or bad 74S89 bipolar RAM chips. That will cause the sound to die out.

The MB3730 audio amp chips are very hearty and I rarely run across bad ones.
 
had a good working Galaga at work that I just so happened to have all the caps for in my case. so I replaced them, because I've seen boards where they go bad. channelmaniac might even remember the time I installed a Bob kit on one and it wound up killing the whole game. :) (long story short, Bob's crap caps were no good)
 
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