Audio only sometimes works

[rancid dust]

Hello! Attempting to mod a GBC with a couple of things.

I bought a GBC that was labeled as non working, but once I received it I found that it powers on, it boots games, and screen works. The only thing that didn’t work is sound. I tried gently scraping at the switch in the headphone jack, and that seemed to get the audio working, so kept going with the mod, testing that the GBC turns on along the way. I also opened and cleaned the power switch.

As I was doing this, I found that the audio sometimes doesn’t work (no boot sound when turning on the console) but sometimes it does. (F2 also seems to be blowing sometimes, not sure if that’s related.)

I’ve checked that there is continuity between pins 4 and 5 on the headphone jack, but not sure what to try next. Thanks in advance!

Mods currently installed

• Giltesa's GBC/GBP USB-C and rechargeable battery mod
• Funnyplaying Q5 Display
• New Funnyplaying speaker

[fair sable]

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Because this post has the "Game Boy Color" tag, we recommend checking out this wiki page https://gbwiki.org/en/consoles/color

[wind patrol]

This should assist.

[rancid dust]

~~Ooh thank you! Some clarification questions:

• For the item suggesting bridging VR1S01/2 to R/LIN, what does "bypassing right/left channel of the volume wheel" mean? What should I be looking for?
• Similar question for bridging S01/2 to R/LIN -- what should I be looking for to know I can rule out filtering issues between CPU/AMP?

Thank you again for linking this!~~

took me a few days for this to sink in! 😅 for any fellow noobs out there that might be reading this, the guide is basically saying these pairs of test points bypass certain parts of the volume system that might be broken. Connecting the test points and bypassing potential broken areas, you can see if the volume behavior changes at all and if it does, you've narrowed down where the problem is occurring.

[rancid dust]

Update! 🎉

1. I fixed the power issue I was having after consulting with Giltesa, and that seems to have taken care of the intermittent audio issue. However, the audio was still a little quiet.

2. I went through the guide and bridging the VR1S01 test point to the RIN test point makes the volume louder!

So now my question is, what's the best way to fix this? I could put a wire between VR1S01 and RIN but is the better way to follow the traces between the two the find where the path is broken? Does this mean the volume wheel itself is faulty?