Repairing a kenwood amp

Check for dry joints. mien had same problem

With your multimeter set to DC volts, the black meter lead on the ground terminal of the amp and the head unit on (so the amp will have remote voltage applied), touch the red lead alternately to the B+ and remote terminals of the amp. If the voltage is below ~11 volts, you need to check the wiring feeding whichever line is too low.