Video Game Repair/Ms. Pac / Galaga Class of '81 Low Sound Issue
QUESTION: Hi Brian,
First off, thanks for your time. I have a 20th anniv. Ms. Pac-Man / Galaga Class of '81 upright machine w/ a 24 inch monitor. I believe it came out around 2001. I noticed you've answered some Qs in regards to similar machines so I was hoping you could help me out with a sound issue.
Over the last half year or so I noticed that the sound was starting to fade. I could still hear it, but it was pretty faint. Adjusting the volume knob by the coin door no longer had any effect on the volume. I then went to the pcb and turned the volume up as high as it would go. This did bump the volume back up a bit, but still not back to full strength. Let's say that on a scale of 1 to 10, the volume maxed out at a 4 with this adjustment. (Adjusting the volume knob by the coin door still had no volume effect either way after this.)
I checked the speaker (8 ohms), and it was near 8. The voltages on the power supply also were within range (5, 12 and 12). That's about the extent of my knowledge with these things, so I wasn't sure what to check next. I'm attaching a photo of the pcb board and also of the wiring just behind the volume knob near the coin doors. I'd be happy to add any other photos you'd need.
Aside from the low volume, everything else on the machine works great.
Thanks again! - Joe
ANSWER: Hi Joe,
I'm happy to help! What it appears is happening is that your amplifier is failing on the board. The sound that is getting fed into it is not being amplified as it once was. There are a couple of things that could be causing this-
1) Those four capacitors that are right above the knob on the board should be replaced. This is likely the cause of the issue.
2) The amplifier itself is going bad. This is less likely, and should only be a last-ditch effort.
3) The potentiometers (knobs) may be flaky, and can be cleaned with potentiometer cleaner (available online in a can) This is also relatively unlikely.
There are a few ways to go about fixing this as well. First, you could have a professional replace the capacitors on the board (or, if you're able to, you). If that's not an option, you could splice in a cheap amplifier into the sound lines for the game and externally control it.
Let me know if you have any questions on how to do this.
Hope this helps,
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QUESTION: Thanks so much for your answer. I've had a hard time locating anyone in my area who could come look at my machine. Knowing what I know now about the capacitors being the likely culprit, is this something where I could take the board to say a local computer shop to make this repair?
Also, if you have a chance, would you mind letting me know how I would go about splicing in a cheap amplifier? Just want to cover my bases.
Ok, i've attached a picture to this that will show how to wire in an amplifier. It's really easy considering that you've got a switching power supply in the cabinet already. You can buy a really cheap amp somewhere like Wal Mart or whatever, or you can buy one even cheaper online.
So what you'll need are two lengths of wire for the power (red and black). Connect the red to the +12VDC tap on the power supply, and the black to one of the GND taps. On the other end, connect them to the respective power inputs on the amplifier. This provides the power. You'll need two more lengths of wire to run from the amplifier to the speaker. Connect each one to the amplifier (as seen in the picture) and you should be good to go. Controlling the volume on the board will be what works- you'll have bypassed the knob on the coin door.
Of course, having the caps replaced is certainly something a computer repair shop can do, and would likely be easier. You should call them and ask how much they charge to replace 5 caps on a board.
Hope this helps!