Robotron Sound Issue

Kegger

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I currently have no sound. It was working then if the machine was on for longer than 10 min.
sound would disappear. Now it no longer comes on at all.
I checked Voltage on the test points and got 4.87, 9.93 and -13.1
I would guess the first 2 are low, would this be a cap issue on the sound board or a power supply problem.

Thanks
Chris
 
Capping the sound card would be the first thing to try.

The other thing would be to trace the sound select signals from the input header through to the PIA and then on to the DAC. If all of that is good, it may be the amplifier.

ken
 
Is the amp chip (TDA2002) working? You can quick/dirty check it by putting a finger on the bottom side of the board where its pins are. Tap the pins of the chip...you should get pops or buzzes if the amp is working. If nothing there, double check by holding a small screwdriver in your hand and touching pin 1 then pin 2 (those are the inputs...I forget which one is used). You should get a good amount of racket then.

http://malzev.tripod.com/comp/images/tda2002.gif
 
Is the amp chip (TDA2002) working? You can quick/dirty check it by putting a finger on the bottom side of the board where its pins are. Tap the pins of the chip...you should get pops or buzzes if the amp is working. If nothing there, double check by holding a small screwdriver in your hand and touching pin 1 then pin 2 (those are the inputs...I forget which one is used). You should get a good amount of racket then.

http://malzev.tripod.com/comp/images/tda2002.gif

I don't normally recommend this. I have heard of perfectly good amps getting fried after doing this. The recommended way is to take a cheap (i.e. RadioShack) soldering pencil and bring it near the amp. The cheap soldering pencils are not shielded and the EMF will cause the amp to buzz, if it is working.

ken
 
Usually on the Williams sound boards there is an actual "test" button that you push to see if it generates any sound at all. I know there's one on my Defender and my Time Warp pin, haven't had to look at my Robotron sound board.

Are you getting anything from that?
 
The sound card reset button only works if the whole system is working (minus the control signal path from the ROM card). If any of the major components is not working the reset button doesn't work either.

ken
 
I don't normally recommend this. I have heard of perfectly good amps getting fried after doing this. The recommended way is to take a cheap (i.e. RadioShack) soldering pencil and bring it near the amp. The cheap soldering pencils are not shielded and the EMF will cause the amp to buzz, if it is working.

ken

What? Its not a cmos IC...there's no risk of damaging it by touching the pins. with your finger.
 
When you said you checked the power at the test points, do you mean on the power board? Be sure to check the power on the sound board, I have seen good power coming from the power supply and not on the board many times. Usually it turns out to be those cheap IDC connectors they used. A while back I replaced all the connectors in my Robotron and it cleared up a lot of issues.
 
When you said you checked the power at the test points, do you mean on the power board? Be sure to check the power on the sound board, I have seen good power coming from the power supply and not on the board many times. Usually it turns out to be those cheap IDC connectors they used. A while back I replaced all the connectors in my Robotron and it cleared up a lot of issues.

I checked at the sound board and the voltages on the +5 and +12 seem low to me.
So I'll cap the board and see what the voltage does. This was always an intermittent problem. I cleaned the board and looked for bad solder joints and everything looked ok.
I replaced all the connectors on the harness for the game so the original connectors are gone. After I cap the board I'll recheck the voltage and see what it reads and go from there.
It seems to do it after the game warms up but right now there is no sound at all. This must be the advantages of owning your own Robotron ;) Thanks everyone for the help, I'll look at other things as I go along.
 
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