Q*Bert losing sound

modessitt

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So - I fixed a Q*Bert a month or so ago, and got the sound back by rebuilding the +12 circuit on the power supply and got the hum to go away by repairing some burnt connectors/traces on the filter board. Everything looked and sounded good while here in the shop. Tested it for about a week and had it on all day while I was here - no problems.

The game has been home for about a month now, and the owner tells me that after the game has been on for about 2-3 hours, the sound will just start to fade away. Cycling the power will get it to come back for a while before fading away again.

I'm thinking I should rebuild the entire sound board (new caps, amp, etc) and maybe the rest of the PS? Is there any other voltage line on the PS that could cause this?

Unfortunately, the game is upstairs and I have no help today, so I was just going to go grab some boards to rebuild here. I'd rather have the entire game so I can test it here, but that's not possible today. I'd like to make sure I bring back anything that I need....
 
Hey Mod, I am in no way an expert and am not pretending to be here.
Though I have had both of my qbert power supply boards rebuilt.

Is the +30 in check?
because mine was not I blew 2 sound boards and had to have them both rebuilt as well.

Oh, and I have been on here for 2 years and your popeye cocktail has been "almost finished" the whole time. :O)
 
Well, I got some help and picked up the entire game. I'll take a look at it tomorrow...
 
The LM379S has two ways it can fail:

- Overheating which can cause something just like you're describing. Doublecheck that heat sink is still attached. Also check the +30V line for over voltage.

- Total destruction - the part fries itself and needs to be replaced.

Bad caps, bad PS... these could also be suspect.

Good luck.

Dave
 
Ok, U23 (LM379S) is missing the heat sink. Considering that the sound works for a while and then fades away (as it overheats), does this mean I can just attach a heat sink and be good to go? Or do I need to replace the chip?
 
I would start by replacing the heat sink and watch to see if it fails again. However, if you don't have time to watch it, I would replace the LM379S, just for good measure and make sure you have a heat sink on it.

Dave

Ok, U23 (LM379S) is missing the heat sink. Considering that the sound works for a while and then fades away (as it overheats), does this mean I can just attach a heat sink and be good to go? Or do I need to replace the chip?
 
The guy's out of town until next week. I'll replace the heat sink and let it run. I'm guessing I'll have to play it a lot so there is sound, because I doubt the overheating issue will be relevant if it just sits there in attract mode with no sound.

Poor me...
 
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