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Ghouls 'N Ghosts bootleg - Sound problem

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daeds

Student
Joined
Aug 3, 2025
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Portugal
Hey there people, long time no see!
I come to you to ask for help in my latest woe, my GnG board is now making this static sound that goes up and down with the gain adjustment pot, I can still hear the in-game sound beneath it but it kind of overpowers it,
This is the board:
gng.jpg

I've checked for leaky caps and all but it seems OK, could be a bad one though, I don't really know where to start looking, it was working before I put it aside,
Thank you!
 
I'm afraid that just checking for leaking capacitors is not enough. You need to check with an audio probe, what sounds arrive to the audio section on the bottom left of your picture and what outputs is generating every time that it goes through a chip or an amp until you find which one is screwing it. Then you know what needs to be replaced.
 
Darksoft said:
I'm afraid that just checking for leaking capacitors is not enough. You need to check with an audio probe, what sounds arrive to the audio section on the bottom left of your picture and what outputs is generating every time that it goes through a chip or an amp until you find which one is screwing it. Then you know what needs to be replaced.
Click to expand...
Sorry for my late response Darksoft, life's been busy as heck lately.
Sadly I don't have any audio probes :( are they easy to make?
Anything else that I can check with minimal tools for now?
Thank you so much!
 
Thats what you need to troubleshoot it. Maybe you can get or borrow oone. Otherwise you can start blindly replacing chips and cpas in the audio section one by one.
 
Darksoft said:
Thats what you need to troubleshoot it. Maybe you can get or borrow oone. Otherwise you can start blindly replacing chips and cpas in the audio section one by one.
Click to expand...
Yeah, really have to get one it seems...
I've tried to get the schematic for this but it's been hard, apart from looking at the traces from the amo where should I begin?
Sorry, I'm still very new to all of this. :)
Thank you!
 
Look for any signs of damage or corrosion. Resistors usually dont break and caps will leak or bump before failing in most cases. I would focus on the amp and any pre-amps, but as I said, with a probe you can hear the sound that is actually coming out, so you should be able to troubleshoot faster and better.
 
Darksoft said:
Look for any signs of damage or corrosion. Resistors usually dont break and caps will leak or bump before failing in most cases. I would focus on the amp and any pre-amps, but as I said, with a probe you can hear the sound that is actually coming out, so you should be able to troubleshoot faster and better.
Click to expand...
Hey there Darksoft!
Today I went and fired the logical probe to check for stuck pins on the audio part, mainly the YM chips, and it was all OK, then, I removed all the socketed chips and cleaned the contacts and the pins with contact cleaner and IPA, it's working now! I'm happy!
Thanks a lot for your time and for your work, I've seen lots of stuff with your name on it and it's a pleasure to have you around helping me out.
Cheers.
 
Well, my victory was not a final victory, round 2!
Seems like the YM3012 chip is the faulty one, when I turned it off and then on after a while same buzzing,
The buzzing goes away if I randomly touch the YM3012 pins with my probe though, and when it doesn't fade it changes frequency, safe to say it's the faulty thing, right?
What can I do? They seem hard to come by. :(
 
daeds said:
Well, my victory was not a final victory, round 2!
Seems like the YM3012 chip is the faulty one, when I turned it off and then on after a while same buzzing,
The buzzing goes away if I randomly touch the YM3012 pins with my probe though, and when it doesn't fade it changes frequency, safe to say it's the faulty thing, right?
What can I do? They seem hard to come by. :(
Click to expand...
APAR has them:
https://www.arcadepartsandrepair.com/store/integrated-circuits/ttl-chips/ym3012/

As for the audio probe, they are pretty simple to make. I made my own using a finishing nail. Simple and cheap. Here'a video on how to make one:
View: https://youtu.be/1GVZWRinypU?si=StEBx2TKb8TIzFhK


Del
 
daeds said:
Thanks a lot Del, sadly I'm from Portugal :(
It's really a gamble to get those chips am I right? I've looked and looked to no avail.
Thanks for the probe video!
Click to expand...
Peter (the owner of that website with the part) is pretty reputable in the arcade scene. So, doubt you would be gambling on that front. The only gamble you'd be making is assuming that the original part is faulty.

My advice: Cobble together an audio probe. You can probably make one from leftover parts you already have. Then your will know for sure if the chip is good or bad.

Del
 
DelsArcade said:
Peter (the owner of that website with the part) is pretty reputable in the arcade scene. So, doubt you would be gambling on that front. The only gamble you'd be making is assuming that the original part is faulty.

My advice: Cobble together an audio probe. You can probably make one from leftover parts you already have. Then your will know for sure if the chip is good or bad.

Del
Click to expand...
Sorry, I meant gamble like finding one around eBay and such. Hehe
It's really weird that the buzz goes away touching pins on the chip, I will try to cobble a probe and off we go :)
 
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