Hi. Check if the supply voltage reaches the amplifier and check voltages with the datasheet of the amplifier, also check if the audio signal is reaching the amplifier, this is tested by welding a cable to each line r, l, etc. which has (only the lines that reach the ampli, not those that are their outputs) and one to ground and solder them to a 3.5 female or male plug or rca (depends on your stereo equipment with which you will test those lines). and if there is no audio signal you must get a manual to check the processor or preamplifier. to check if the amplifier is doing the amplification, do the same but now inject the audio signal (connect the 3.5 plug to your cell phone) but you must remove the capacitors or resistors that are in series with each line (it is not to damage the preamp or processor) greetings, I hope and serve you