Robotron Sound Problem ... Getting Warmer

SteveJ

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Jul 15, 2009
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Purcellville, Virginia
My Robotron is missing some sounds, and others are incorrect. Based on advice from here, What I've done so far:

1. Adjusted switcher voltage (it drifted to 6V -- this could have caused it)
2. Checked Cable continuity between ROM and Sound boards
3. Replaced IDC connectors with Molex
4. Installed Bob Robert's cap kit on Sound Board

I researched the ROM/SOUND interface, and tested the pin headers on the sound board. Basically, by grounding each of the pins, a certain sound is generated (this is what the "sound lines" self-diagnostic does). If each pin works, then theoretically, the combination of pins will work as well.

So I grounded each pin in turn, and when I got to pin 7 (sound line 5), The sound would not turn off, even when the pin was "ungrounded". The other sounds shut off as soon as I removed ground.

First question: Is this normal, or is my pin #7 sticking "low"? If so, could this be the 6802 or 6821 on the Sound Card?

Second Question: I'm not sure what "normal" sounds should be for these tests... has anyone posted (youtube or wav file somewhere) what a functioning robotron diagnostic sounds like? The troubleshooting material only says "makes a sound", but obviously that isn't good enough in this case.

for example, what sounds should come out when the sound board self-diagnostic switch is pressed? What sounds should the "sound line" diagnostics make?

Any help is appreciated, I'll try to trace through the boards and see where pin 7 leads me.

If I get this fixed, I'll record and post the working sounds myself :)
 
have you replaced the sound rom yet?

Oh yeah, and aren't there specific jumpers needed for that sound board that other games had different? Just in case this sound board was not an original Robotron sound board...
 
Have not replaced the sound rom yet, have just ordered one from hobbyroms... replaced the 6802 on the sound board, and the 6821 on the ROM board. I have an extra 6821 for the sound board if the sound rom doesn't do the trick -- the thought of desoldering 40 pins doesn't sound appealing at the moment. :)

thanks
 
have you replaced the sound rom yet?

Oh yeah, and aren't there specific jumpers needed for that sound board that other games had different? Just in case this sound board was not an original Robotron sound board...

I know there's jumpers for the ROMs.....2716s versus 2532s.....
Jumpers for the processor/RAM...6808/6810 versus 6802...
And a jumper for a speech board....with or without

Edward
 
Robotron Fixed

Thanks for the help everybody. Taking the shotgun approach, I replaced just about everything on the sound board until it worked.

It was the 6821 (PIA) on the sound board.

I put off replacing the PIA until last, because it looked like such a bear to replace. I wasn't wrong about that... took me almost an hour to desolder the chip and clean up all the holes. Once done, I said "never again" and put a socket on there :). Once I put in the new PIA (from arcadechips), I resoldered some cold joints on the header pins... and voila! My robotron sounds great again.

The real moral of the story is troubleshoot the right way with the right tools -- which of course, I didn't do. I'm definitely going to learn how to use a logic probe.

On the bright side, I have a completely rebuilt sound board and I did need the practice soldering. I think I have enough confidence to do it right next time.

Thanks for helping me out!
 
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