Missile Command with sound problem

Chris5467

New member
Joined
Feb 1, 2024
Messages
5
Reaction score
1
I recently acquired a Missile Command arcade. In every other way it works perfectly - except the sound. The sound is low and cuts in and out (kinda of starts at medium volume and drops off then comes back). There is no static or noise - the sound is perfect just never loud and each effect (explosion or whatever) starts at a medium volume then drops off to almost nothing... Looking at the AR board - seems like the previous owner replaced alot of the parts - capacitors are shiny new. The other board (main board?) has some weird daughter sockets (a socket plugged into the board socket, and then a chip is plugged into the daughter socket). Not sure if that is legit or not. Any one have any leads on how to troubleshoot?
 

Attachments

  • Missile Command Main Board.jpg
    Missile Command Main Board.jpg
    770.7 KB · Views: 9
  • Missile Command AR Board.jpg
    Missile Command AR Board.jpg
    364.9 KB · Views: 11
It could be a dirty volume pot. What happens when you adjust the volume pot? Does the cutting out of the sound change or stay the same?
 
Adjusting the pot changes the sound smoothly as it should. No pops or crackles. But even at the highest setting - it's still not as loud at it should be. And at any pot setting, the sound volume isn't consistent - bouncing up and down in volume.
 
It could be faulty TDA2002 amplifylers on the AR-II or LM324's on the game board.

Do you have another AR-II you could try swapping?
 
I don't have an extra AR-03 unfortunately - only an AR-02 from a friends machine -will that still be able to test the audio?
 
So I cleaned up some solder points and reseated chips... The sound is steady now but still very low. Also I've noticed that on startup sometimes it won't register the 1P or 2P buttons (so I can't start a game). After fiddling a while (rebooting a bunch of times) it seems to work for a while but then comes back...
 
So I cleaned up some solder points and reseated chips... The sound is steady now but still very low. Also I've noticed that on startup sometimes it won't register the 1P or 2P buttons (so I can't start a game). After fiddling a while (rebooting a bunch of times) it seems to work for a while but then comes back...
Looks like there may be two separate problems going on here. The sound is likely unrelated to the button problems.

I was taking a closer look at the picture of your AR. I'm not too sure about the solder work on it. It looks like whoever replaced the diodes, didn't heat up the through hole enough to let the solder flow all the way through. It makes me wonder what the solder side looks like.

Missile Command AR Board.jpg

It sounds like you are getting audio from the game board. It is just not coming out the speakers at the correct volume and is being distorted. As far as I know, there is no easy solution to figure out the problem. I can see four potential causes. Starting from the output and working backwards,
1) blown speaker
2) faulty volume potentiometer
3) bad TDA2002's on the AR
4) bad LM324's on the game board.

It would be easy enough to test the speakers by temporarily swapping out another speakers (I don't think this is the problem). You stated that the volume pot doesn't change the messed up sound when it is adjusted (I don't think this is the problem either). You said that there was extensive work done the AR. This, and the questionable solder work, leads me to believe this is the most likely a problem. How are you with your soldering skills?

Maybe someone else on here has a different opinion.
 
It could be the LM324. Low and crackly would make me want to test that first since they are such high failure components.

 
Back
Top Bottom