Low audio output on Twin Famicom AN-505-BK

[waterclocker]

Hey all, I recent noticed that my audio level is really low on my Twin Famicom AN-505-BK.
I also have the AN-505-RD that I recently picked up and it works great, but it make me realize
how much lower the audio is on my AN-505-BK.  I tried swapping the output boards between
the systems and there was no change.  That means that the issue is somewhere on the main
board.  Maybe a transistor or resistor is going bad or the value needs to be changed.  I didn't
notice any difference between the boards.  Anyone have any suggestions or deal with this problem
before?  I might just have to trace out the audio circuit and test the components.  Does anyone
have a diagram of the Twin Famicom audio circuit?  Thanks!

[hvc01]

audio circuit is pin46 on cartridge connector that's it. http://jpx72.detailne.sk/modd_files/fc/avmod.htm see step 8

[famiac]

This may be helpful:

http://www.sega-16.com/forum/showthread.php?20737-Repair-Log-Sharp-Twin-Famicom/page3