PC-Engine Duo-R Audio buzzing.

I have a RGB modded PC-Engine Duo-R. The caps have been replaced. The audio buzzing changes depending on what's on the screen. The RGB Scart cable came from www.retrogamingcables.co.uk. I have connected all the grounds on the Scart. The buzzing is very loud and distracting..

Here's an example of it, letting Paranoia play itself for just under a minute.

https://www.dropbox.com/s/gw7q9ono3skx5xx/pce record.mp3?dl=0

Any help would be greatly appreciated. Thanks.

 

I'm assuming the jack has been replaced on the back with an 8pin din? Can you take some pictures.

 

Obviously first of all check all your sodering. Is the buzzing present with composite cables? Is it possible to open the din 8 plug and check that everything is where it should be? I have found that having just the outer grounds (pin 21) connected to the shielding in the cable and all the other ground points separate from this helps on some consoles.

 

I did replace the socket with a 8pin din, yeh. The buzzing occurs with composite cable as well as scart. I've triple checked all my soldering, and its fine. I have replaced the caps on audio again, and no difference. I've tried removing the rgb amp and no difference. The console does it by default. I've checked the power lines, and its all great. Spot on in fact. I've tried different power adapters. I tried adding a resistor to audio ground, no difference. im running out of ideas. :/ Im starting to wonder if its actually the m5205 audio chip itself...

 

I really don't think the M5205 is at fault. My suspicion still is your RGB cable, I've seen pics of the cable maker and is not fully shielded.

Now, are you plugging the cable directly into a scart input or is it going into some sort of converter?

 

When you say you have checked the power lines, I assume you just mean with a multimeter?

That will not show noise, only an rms value.

 

If it was my scart cable, would it still occur on the original av rca cable? Because it does. I even went console - cable - headphones, and same deal.

Yeh. I need an oscilloscope.. Not that I'd know how to use it.. I do want to learn how though.

EDIT: So, update! It seems the buzzing only happens when using the turbo everdrive! I tried normal hucards, and they were silent. I tried taking the RGB amp off completely and used the turbo everdrive, and still had buzzing, also.

EDIT: I should have tested more. So.... With the RGB amp connected (the R, G, B lines connected to the output socket), I get buzzing on everything. With the RGB amp not connected (R, G, B lines floating in the air on from the output socket), buzzing still occurs on the Turbo Everdrive, but not normal HuCards.

EDIT2: OK... more specific info... It only occurs if video is being output. Sync issue? Composite interference?

 

Sounds like unshielded audio lines in your SCART cable.