Coxx GG-30 with low volume issue

[joecool85]

SOLVED!

Sorry for long time without update. I received the LM1875 today, I changed it and the problem was still there   
I decided to remove the surrounding capacitors and measure them one by one. It turns out that C12 was damaged, but not in short so I didn't detect it before. It measured some kohm in resistance and 0,5 uF instead of 4,7 uF. That damned capacitor drove me crazy.
Anyways, I changed it and the amplifier is now loud again.

I would like to thank a lot everyone that helped me, in particular dmeek that made a lot of work with reverse engineering.  Without the shematics I would have been lost. I hope that these posts will help people with the same amplifer.

Good job!