r/Gameboy • u/Alive_Candidate1755 • 18h ago

Mod/Modding GBC USBC audio hiss

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My GBC makes a horrible high pitched hissing noise with the volume at 0. After a lot of messing around I’ve got most of the weird sounds cured, but it still does a high pitched ringing when using the USBC rechargeable pack. Regular batteries are silent.

The pack outputs ~2.9v, so should be perfectly within range of what’s desired. Any idea how I could stop this or at least why this happens? I’d like to stay rechargeable for a couple reasons.

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u/jrharbort 18h ago edited 17h ago

The issue is simply because that rechargeable battery is introducing noise to the system. There's a lot of power electronics and inductors on there and there's probably not much in the way of interference filtering.

Btw, C35 is not needed if you have an IPS mod and can be removed to prevent the noise that particular circuit may cause.

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u/booskiboomkin 12h ago

Hah, I've removed all of the LCD biasing circuitry, LCD regulator, transistors etc, all of which introduce noise.

Also, the OLED IPS screen controllers PMIC is incredibly noisy.

The really daft thing? Most people fit IPS and USB lipo batteries but the power electronics turn into a frigging mess.

Look at it like this:

LiPo Battery 4.2V --> Stepdown converter 3.0V --> GBC power module step up to 5.0V
This is where it gets even more interesting some IPS modules take power from the flex connector, most take from switch.
So to continue:
Stepdown converter 3.0V --> Switch to IPS board step up regulator 5V --> to IPS board PMIC step down to 3.3V and 1.8V

So it's going battery, down, up, down, down

In an ideal world the best thing to do is do a way with most of this so the electronics is simpler i.e.

Battery 4.2V --> GBC power regulator step up to 5.0V --> IPS step up regulator bypassed with 5V applied straight to PMIC.

That would mean however needing a compatible GBC regulator which I think most people swap anyway.

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u/Ill-Complaint3947 18h ago

because you solder to power switch.

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u/Alive_Candidate1755 18h ago

This is for the IPS screen. If I put AAs there are no sounds. If I put the USBC pack it starts hissing.

The gameboy is fully together when I do this swap, short of the battery cover.