Defender -No Sounds-

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Hi;
I searched all posts relating to missing sounds and have come to a road block.

Originally I had both, ROM error and missing sounds but have repaired the ROM error by replacing the #10 ROM socket and ROM PCB ribbon cable. I also chksum the #10 ROM and it comes up AFC4, just to make sure.......

Back to the missing sound......

I have the "longer" sound board.
I checked the fuses - OK.
I checked the caps for shorts / open - seems OK
I tried grounding 10J3 pins to GND and did not receive any sounds
I get the "crackling" through the speaker when running the volume pot so the speaker and amp seem to be working as well......

Does anyone have any suggestions or are there any other tests I could perform to try and isolate the problem?

ANY help appreciated.
Thanks in advance
Jeff
 
Hi Jeff,

Pull the schematics and use a logic probe to walk the signals from the data socket pins all the way through to the PIA. You may have a bad PIA or you may have bad buffer chips not letting the signals through.

ken
 
Ken;
I probed and traced through the PIA which was bad.
I replaced the 6821 and did a cap job as well. I fired it up and still no sounds!
I hooked up my neg probe clip to the neg side of C27 (where I tap power for the probe) and the sounds came to life, (before I had the chance to hook up the pos clip).
I played about 9 games, loud and clear and then the sounds went out again.
BTW, I get a ROM error when I first boot the game but after about 3 min, I reboot and there is no longer a ROM error. I place the game into test and all tests (ROM, RAM, CMOS etc) pass..... The game is currently in my garage, (cold) so I am going to bring it into my shop, (warm) and see it that effects the first boot.
One other thing, after my first game after I had repaired the sound issue, I noticed that it had 39 credits on the game. I had to manually coin up the games before that. I played it down to 28 credits and thats when the sound dropped out again.
I am going to bring it into the warm before I continue to troubleshoot.
1-Why do you think the sound came to life when I clamped the neg lead?
and
2-What would cause the credits to self "credit"?
Peace
Jeff
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Hi Jeff,

Which PIA did you replace the sound card one or the ROM card one?

C24 on which board? It is possible that either the through hole plating is cracked or the solder joint is cracked and when you attached the clip it wiggled the wire and made contact for a while. You might try reflowing the solder on both sides.

The 39 credits sounds like a CMOS glitch. It may have been just a shutdown issue (see my rants on switchers and Williams games). Hopefully that will only be a one time issue.

ken
 
Ken;
All the work I did was on the sound PCB, replaced all caps,(electrolytic) and PIA.

I will check the card once I get the game in the warmth and see if I see a hairline crack of something.

Thanks
Jeff
 
Sounds good. Don't forget to let the tube warm up for at least an hour before you power it up. I have heard bad things can happen if you power up a tube when it is cold.

I am looking for the old sound card schematics. I know I have a copy, but I have yet to find where I stashed the file.

ken
 
Ken;
Happy New Year!
Don't bother looking for the schems, I think I got it.
I'll elaborate tomorrow.
Peace
Jeff
 
Hi Jeff.

That sounds good. I hope it was something, simple/stupid that I overloooked.

ken
 
Ken;
I think that the really cold enviroment had a bearing on the operation of the game. I brought the game into my shop, let it warm up for about 4 hours and tried again. I am happy to say that the sound is working properly now.
I then had another problem, no response from half of the controls when playing!
I placed the game in test and tested the switches and had an interesting display, most of the buttons were energised and I had 4 "unreconizable switches" - I think that what it displayed......
Anyway, I found that the ribbon cable to the widget was bad. I had a spare widget and relaced the exising and now, (knock on wood) everything seems to be working great.
For a game that I thought was working correctly from the beginning, there was sure a lot of repairs that were necessary!
Peace
Jeff
 
Sounds good. Don't forget to let the tube warm up for at least an hour before you power it up. I have heard bad things can happen if you power up a tube when it is cold.

I am looking for the old sound card schematics. I know I have a copy, but I have yet to find where I stashed the file.

ken

killed a Polo like that 2 years ago. it's still dead, after 3 repairs.

live and learn. :)

I need to sort out my Defender sound card one of these days... I got sound, but wrong sound.
 
I was going to work on my Silent Scope II but now I'll have to wait until I either bring it into the shop or the weather gets warmer, that has a super nice WG and I would hate to damage that one!
Jeff
 
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