Help with Jamo A3Sub3 LM3886 output

[marcelomorais]

I bought a second hand Jamo A3sub3, but it has very low volume to the subwoofer, i tried replacing the lm3886 but no sucess.

I suspect that it doesnt go off mute, voltage at pin8 os -32v, the transformer is 32v-0–32v

Is it ok that voltages?

 

[tomchr]

The voltage on pin 8 (mute) of the LM3886 is generally about 2.5-3 V. If you look at the equivalent circuit on page 7 of the data sheet you'll see that it's basically three diode drops + Imute*1kΩ away from ground. If you're seeing -32 V there the LM3886's mute circuit is probably blown. I wonder if Rmute short-circuited. See the Typical Application schematic on Page 2 of the data sheet.

Tom