Williams Defender doesn't have sound...HELP!

woodsy169

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Ok, bought a working Defender, had sound, everything worked great. Played several games one day, turned it on the next and the controls were a little flaky, turned it off, reseated the ribbon cable and the controls worked again...ok, so I turned up the sound, not full blast by any means, but it was loud. Played several games over several days, then one day I turned it on and it didn't "growl"...no sound whatsoever and haven't had any sound since. Turning the volume pot up, you can hear a hum in the speaker get louder or quieter as you turn it down, so it looks like the sound amp is working. Figured since I was ordering a new control ribbon cable from Bob Roberts, why not order a new volume pot and a sound card cap kit since it seems that other KLOV'ers with the same issue as mine, resolved the sound problems by installing a cap kit. Ok, so I installed the new pot, same issue, installed the cap kit (except for the three small caps, the ones on my sound card didn't seem to be the same value) and still no sound.

Any ideas on what I need to do next? Hoping to resolve this soon...I miss my Defender sounds! Reminds me of the local pizza place when I was a kid...
 
At this point, it looks like you will need to break out the logic probe [cue the booming LOGIC PROBE echo effect] and the voltmeter.

First step is to always check to make sure that you are getting the correct voltages. It could be as simple as a blown fuse. The schematics will have the voltages at the test points. If you don't have them, the drawing sets are available at http://arcarc.xmission.com.

If the voltages check out, then you will need to follow the signal path with the logic probe to look for any bad chips. Start with checking to make sure you are getting clock signals (check the schematics for a good place to test for this) and check for address and data line activity. These would indicate the CPU is working.

Next use the logic probe to test the signals on the parallel cable from the ROM board to the sound board. There are 7 lines on it. Just put the game into the diagnostc tests and go to the sound test. Make sure it is cycling throught the sounds. Then use the probe to watch to make sure the lines on the cable are toggling.

If they are good, then pick a data path and trace it to the PIA and then to the DAC. If the signals go all the way to the DAC, the DAC is bad and it will have to come out. Likewise if the signals stop in any chip along the way, it will need to be replaced.

ken
 
Issue

I've got kinda the same issue with my robotron.. Have you tested the sound pcb in another game? Ive got no sound in my robo, tested the pcb in my joust and it works fine.. I also replaced the pot and checked the speaker..

Something tells me it's the rom pcb.. If you can, try testing it in another williams game..
 
Found this problem with my Defender...check the wire harness to the speaker. There is a connector at about half way (next to monoitor) to the speaker. mine had a broken connection there.
 
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