Losing (Lost) Sound on Qbert

Phetishboy

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Well it finally happened. My sound is going out on my Qbert. I have Doyle's newest kit installed. The sound is there for 5 minutes, then fades and dies. Power it back up and the sound is there but fades again. I have replaced the sound chip on the main CPU. The filter board has been re-flowed. This soundboard's solder joints were re-flowed and U16 replaced. I have not yet replaced U17, could that be it?
 
I'd uninstall the kit, just to eliminate it a as a factor. When you say it "fades and dies", do you mean it works 100% then quits? Do you have all the voltages there when this happens?
 
Check the power supply....if the 30 volts drops, youer sound will go out....cold sodler points on that power supply and also on all those capacitors! Reheat all of them...a leaky cap could also do that (on power supply) Todd from TNT Amusements
 
I'd uninstall the kit, just to eliminate it a as a factor. When you say it "fades and dies", do you mean it works 100% then quits? Do you have all the voltages there when this happens?

Yep 100% sounds, then it fades out and is gone. Haven't had time to check voltages yet.
 
Most likely you have the same problem as the one I fixed that had the same issue. game would start up just fine, but then after a while the sound would fade out. Turn it off for a bit and then turn it back on and sounds are back for a while before they fade out again.

Look at the sound board. There is a chip at U23 that should have a heat sink on it. If it does not, then that is your problem. As it heats up, it ceases to function, then when it cools off it works again. Adding a heat sink to mine fixed my issue for good.

However, if it has been damaged by the overheating (adding a heat sink doesn't help), you may need to replace it - and add a heat sink to the new one...
 
i'd start with that 470uf 35v (C36) as a fun test and see if installing a new cap fixes your problem. or you could replace all the electrolytics on the sound and speech assembly as they probably have dried out quite a bit by now and are in need of replacement.

heres the manual if you dont already have it.

http://www.tamdb.net/index.php?page=ManualDetail&id=3013

at least if replacing them doesnt fix it, you can cross them off your list as a potential problem.

cant tell you how many times that has fixed a no sound problem.
 
Hook a meter up to the +30v line and monitor it. If its holding steady when and after the problem occurs I would recap the sound board.
If that LM379S doesnt have a heatsink it could definitly cause this but usually it would fry without a HS in a matter of minutes.
If you find the +30v is going off spec, try replacing D26 Zener diode on the power supply. Keep in mind that when you first turn on the machine it is normal for the 30v to start out around 29v and increase to around 31v as the components on the power supply heat up. This is assuming you have a 30v zener. If 27v zener, it will get up to around 29-30.
 
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If that LM379S doesnt have a heatsink it could definitly cause this but usually it would fry without a HS in a matter of minutes.


While that's certainly likely, the one I had here did it like that for over a week before I got on here and someone told me to check the heat sink. I had the game running about 6 hours a day for a week before I figured out that was the issue....
 
While that's certainly likely, the one I had here did it like that for over a week before I got on here and someone told me to check the heat sink. I had the game running about 6 hours a day for a week before I figured out that was the issue....

I dont doubt you one bit. Just saying that running it without a heatsink is playing with fire and it will fry eventually if not in the first few minutes. You just got lucky.
 
Haven't had time to mess with this yet, but I have to check why the knocker isn't working, why I have static on the screen, and these sound issues. Man I hate messing with games that were supposed to be 'restored'. Will a fan help dissipate the heat in this sucker?
 
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Sometimes just leaving the backdoor open and pulling the disconnect switch out will help. Alot of heat comes off the power supply board.

It does sound like something is wrong with the LM379 chip, or the 30V that supplies it, from what you mentioned so far.

Luke
 
Phet,

What did you end up finding out about this problem? I have the exact same problem. Already rebuilt the sound board but no luck so far. Got more components on order to shotgun some more of the board but I'm just trying to get lucky and find it at this point.

Thanks!

Jeff
 
I replaced the chip at U17, which fixed it, but then I started having issues again so I installed the arcade shop switcher. That pretty much cured it, but now my multi kit is having issues.
 
I replaced the chip at U17, which fixed it, but then I started having issues again so I installed the arcade shop switcher. That pretty much cured it, but now my multi kit is having issues.

Glad you fixed it. I have that part on order from Riptor so hopefully that will help mine. Bummer with the multi-kit. Did you email Mike D. yet? He's pretty good at helping with those things.
 
Glad you fixed it. I have that part on order from Riptor so hopefully that will help mine. Bummer with the multi-kit. Did you email Mike D. yet? He's pretty good at helping with those things.

Yep, we've been in touch. He asked me to send him the kit and he will take a look at it. I'm sending it to him tomorrow. Great guy.
 
Yep, we've been in touch. He asked me to send him the kit and he will take a look at it. I'm sending it to him tomorrow. Great guy.

Since I finally got a Q*bert I need to pick up one of those kits. I've been trying to decide whether to get that or a JROK kit. Both are really good. I already have a mostly working game so I'm leaning towards Doyle's kit.
 
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