At an integrated AMP I would measure the supply Voltage an current.
Then check the Capacitators and voltages at all of the pins of the chip - Vompare that with Data Sheet.
12V, 2 x 8 Watt
• Mute mode • Thermal protection • Short-circuit proof
If the DC volume control voltage falls below 0.4 V, the device will switch to the mute mode.
The amplifier is a short-circuit protected to ground, VP and across the load.
A thermal protection circuit is also implemented
When you hook it up and try to use it, what happens?
Does it heat up to touch?
Is this home made (has this ever worked) or commercial product?