Robotron - no sound

Spyridon

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Sound stopped working today on my Robotron. Sound board had been recapped and everything was working fine. Today when I turned it on...nothing. Fuses are still good. Any thoughts on what to check first?
 
Got to thinking about it and you could also pull the power connector for the sound board and test the voltage at the connector to see if the problem is in the harness or on the board.
 
Are you sure volume is totally gone? Have you tried cranking up the volume to verify?

I had an issue with very low volume on a system 6 pinball sound card, essentially the same board I think (speech was fine). I changed out, in order, C29, C28, then Q2 to resolve it. It wasn't until Q2 was changed that the volume levels came back to normal.

May not be related to your issue though.
 
Are you getting the "William's Humm" on startup? If not, the amp may have crapped out. I have found these often go south after new caps have been installed.

If you have an old style pencil type soldering iron, try bringing in near the amp chip while is it plugged in and the sound card is powered up. That should induce enough 60Hz into the amp to cause a hum in the output.

If it needs to be replaced, Jameco has TDA2002s (direct replacement), but GPE has TDA2003s, which are a higher wattage version.

ken
 
reflow the headers on the sound board and retest the voltages

Done. No change.

Got to thinking about it and you could also pull the power connector for the sound board and test the voltage at the connector to see if the problem is in the harness or on the board.

Voltage at the connector matches the power supply which has +12v at about 9.56v. How important is the +12v for the sound? It drops to 8.36v on the sound board. However, if I swap the power supply with the one from my Sinistar, even at around +10v at the sound board, I have no sound.


Are you getting the "William's Humm" on startup? If not, the amp may have crapped out. I have found these often go south after new caps have been installed.

I'm getting the "William's Humm" on start up. Can I assume the amp is good?

These are notorious for crapping the sound ROM too. and a few other things out of the blue.

Okay, what's the best way for me to start checking the ROM and other things?
 
The big 40 pin socketed chip...or as Dokert likes to call it...the CPU! ;)

This was the problem with mine.
 
Try pressing the diagnostic switch on the sound board. It should play one of the sounds over and over again. Given the current state it may not, but if it does, then it will probably be in the interface section. It may take a session with a logic probe to sort it out.

By the way, if it does work, the only way to shut it up is to power down and back up.

ken
 
Try pressing the diagnostic switch on the sound board. It should play one of the sounds over and over again. Given the current state it may not, but if it does, then it will probably be in the interface section. It may take a session with a logic probe to sort it out.

Pressing the switch has no effect.
 
The big 40 pin socketed chip...or as Dokert likes to call it...the CPU! ;)

This was the problem with mine.

Are you referring to the socketed chip on the bottom left?
IMG_8242.jpg


Maybe I can swap in the one from my Sinistar and see if that fixes it?
 
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