Galaga Speaker Hum

barrysfarm

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I apologize if this has been asked before. I'm not quite sure of the search terms, so that makes it hard to search.

I'm getting a noticeable, to the point where it's a bit annoying, hum through the speaker. I've turned off the monitor (& the marquee light isn't hooked up yet) and nothing changes. The game plays fine, no problems there. The speaker itself is original, but the harness and the entire power supply were replaced with new ones. The hum is much louder than on my Ms. Pac. There's a hum from the monitor too, but it's not that bad.

Where should I start looking? I don't think there's interference from the monitor. I built the power supply piece by piece, using mostly Bob Roberts parts. The distribution block, and the fuse block is radio shack.
 
The three right under the sound amp are a good place to start - especially the larger one in the middle.


Bill

Caps on the pcb? Thats where I would start.
 
If it's noise when the game is playing, then recap the audio section.

If it's noise when the game is going through self tests when first powered up, it's normal. Galaga boards make all kinds of different noises - each one different - when first starting up. I've seen boards that make high pitch squeals, low pitch hums, and other noises in-between.

RJ
 
If it's noise when the game is playing, then recap the audio section.

If it's noise when the game is going through self tests when first powered up, it's normal. Galaga boards make all kinds of different noises - each one different - when first starting up. I've seen boards that make high pitch squeals, low pitch hums, and other noises in-between.

RJ

It's a consistent hum whenever the machine is on.
 
Are any sounds missing?

If not, recap the audio section. If yes, then you may have a problem in the digital logic section for sound.
 
I've fixed hum several times by replacing the audio amps. In my experience, this is more likely the case than caps.

I don't know what amps Galaga uses, but if they're TDA2002's, replace the amps. You can get them from Bob Roberts, and it's worth keeping a couple of spares around.
 
Isn't there a no-abandon-your-thread rule at KLOV? Well there should be! Where did this leave off? :-D

The Galaga still hums. I replaced the audio caps, but didn't make a difference. The machine is in our office and gets played about once every 3 months, so I'm not worrying about it anymore. However, the 2-way joystick won't return to center anymore. If someone knows a place where I can order a new 2-way stick that will fit an original galaga, let me know.
 
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