Scramble volume level auto adjusts

treborlicec

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Hi all. On my Scramble, the volume level auto adjusts during game play. Starts out at the level I want, then gets lower and comes back, etc. Never cuts out. Is this likely the caps or the pot? I searched other Scramble repairs, but couldn't find my issue.

Thanks,
 
No thoughts? I'll probably change out the caps on the sound pcb since they are original, anyway.
 
IF no one else posts with it, yes. I can pull a board and look, howver, not off the top of my head. I'm in and out all day today...but would be happy to help you out when I get back to the ol' bench. :)
 
I've reflowed the amp and pot and I shot a little contact cleaner in the pot and wiped it back and forth a bunch. The sound issue is more specific than I originally thought. The bomb sound gets louder than the rest of the sounds. Now, I'm not sure if the bomb sound is getting louder or if it starts out soft and gets to normal volume. I can't find any markings to tell me the value of the pot. It's VR200, but I can't find any reference to the value of this pot.
 
Treating carbon pots with contact cleaner is a bad idea. Contact cleaner is too aggressive. It destroys the carbon. :(
 
Treating carbon pots with contact cleaner is a bad idea. Contact cleaner is too aggressive. It destroys the carbon. :(

Well crap. I thought I saw or read where that can help. Now I really need to know the value, so I can replace it.
 
New pot didnt fix it but it was only 60 cents lol. Ordered an amp. Fingers crossed.
 
OK, so I've now replaced the pot and the amp and no change. The bomb sound, and only that sound gets louder and softer on its own. Could this be a cap issue or logic/roms since it's just the one sound?
 
check the section shown in the attached pic (on the upper soundpcb)

because it is only 1 sound (one channel?) affected, it could be there...

there are 2 software-controlled switches for each output channel of the soundchip that switches the output through a capacitor to ground (filter ?)


either
->the capacitors (0,22 uF / 0,047uF)
->the MOS 4066 switch at pos. 7g/7h
or
->the LS 74 Flip-Flop at Pos 7f / 6g / 6h

_might_ be the problem
 

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check the section shown in the attached pic (on the upper soundpcb)

because it is only 1 sound (one channel?) affected, it could be there...

there are 2 software-controlled switches for each output channel of the soundchip that switches the output through a capacitor to ground (filter ?)


either
->the capacitors (0,22 uF / 0,047uF)
->the MOS 4066 switch at pos. 7g/7h
or
->the LS 74 Flip-Flop at Pos 7f / 6g / 6h

_might_ be the problem

Thanks, I'll check that stuff. Also, I decided to check my Scramble voltage and the edge connector was 5.0 even. The switcher read 5.46!!!! Chips on the bottom board read 4.6. That's a big drop. Cleaned the edge connector and used some sand paper to get some of the oxidation off of the harness connector pins (in the connector, not on the board) and it didn't change anything. Could that huge voltage drop cause this sound issue, by chance?
 
check the section shown in the attached pic (on the upper soundpcb)

because it is only 1 sound (one channel?) affected, it could be there...

there are 2 software-controlled switches for each output channel of the soundchip that switches the output through a capacitor to ground (filter ?)


either
->the capacitors (0,22 uF / 0,047uF)
->the MOS 4066 switch at pos. 7g/7h
or
->the LS 74 Flip-Flop at Pos 7f / 6g / 6h

_might_ be the problem

This guy seems to know Robert... ;)
 
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