PC Engine Duo audio problem

[Ergot_Cholera]

I have a Duo with audio issue. I have replaced all the capacitors but the issue persists. There is no audio on Hucard games via a TV but the audio is present but very quiet through the headphone socket. The CD audio is present on both TV and via headphone socket but again is very quiet and scratchy.
Could it be a problem with IC 506? If there is a bad trace/via then there would be no sound at all, would there?
I have another (dead) Duo board that I can use to salvage parts, although there is no knowing whether these parts are damaged too.
It would be nice to make one fully working console from the two I have with faults.

[pnauts]

probably damaged trace or via.
cleaning needed.

[Ergot_Cholera]

Correct, it was a via near C322. Although there are still some issues with the headphone socket. The volume dial (potentiometer?) only controls the left audio and the right remains full, plus the audio from the AV socket continues to play when headphones are inserted in the headphone socket.
I teted some of the nearby vias and found that neither of the vias leading to/from C884 were connected, I connected them back up and noticed no difference.

[bozo55]

... plus the audio from the AV socket continues to play when headphones are inserted in the headphone socket...

I think that's normal, that's how mine is.

[Keith Courage]

plus the audio from the AV socket continues to play when headphones are inserted in the headphone socket.

This part is correct. However, if the audio doesn't turn down in one side of the headphones then a new volume wheel needs to be installed.

[Ergot_Cholera]

plus the audio from the AV socket continues to play when headphones are inserted in the headphone socket.

This part is correct. However, if the audio doesn't turn down in one side of the headphones then a new volume wheel needs to be installed.

I had nothing to compare it to so I assumed there was a problem, as stereos etc. will cut out the main audio out when headphones are inserted.
If the AV socket audio continues to play then the headphone socket is basically pointless isn't it?
I will transplant the volume dial from my spares Duo board and see if there is any difference. This one is worse.
 I will need to buy a replacement, can anyone tell me the resistance?