I don't know what I did wrong on this amp.

[Hextejas]

I have 2 of them and 1 works and the other doesn't. They are based upon the LM3886.
I have done nothing more than apply power to them and then take voltage readings at each of the 11 pins. Plus the heat sink.
I know that board A works because I inputted a 1khz sine wave and I could hear it from the speaker. Board B is silent.
So here is the schematic and the voltage readings. The HS reading was to the heatsink which touches the metal tab on the LM3886
I checked the soldering and it looked ok to this newbie eye. So, I was hoping  that someone would take a look at the schematic
In relation to the different pins and say AHA!, here it is.
Pin...A......B
1......31....31
2.......0......0
3.......0....-10.8
4....-31....-31
5.....31....31
6.....0......0
7.....0......0
8....-3.....-3.5
9....-30....-10.8
10...-1.8...-10.7
11.....0.....0
HS...-31....-31

I am forever in your debt.

[Stuart Coyle]

I would check if the Zener on the mute output is actually dropping 16V, and make sure that there is more than 0.5mA going through the 10k resistor. Just a guess, but maybe the mute is active. 

[Stuart Coyle]

Oh, and the other obvious thing to do is swap the amplifiers in the two boards, then you know if it is the board or the amplifier chip which is at fault.

[Andy Watson]

The voltage at pin 3 is wrong - there should be a connection (somewhere) between the signal ground and the power ground.
Perhaps post photos ?

[Hextejas]

Thank you Andy and i will check closer when i get home.

[bson]

Check PWR_GND vs SIG_GND; the input voltages are completely borked.  Check the supply rails.  Does anything get hot - what is the idle current consumption?  Maybe you reversed a power header or something.

[Hextejas]

Check PWR_GND vs SIG_GND; the input voltages are completely borked.  Check the supply rails.  Does anything get hot - what is the idle current consumption?  Maybe you reversed a power header or something.

Thank you bson, I will do what you suggest. But I don't quite know how to do what you suggest.
PER_GND vs SIG_ GND
Using a meter, how do I measur it ?