I swapped out the audio amplifier (TDA2030AL) and the two transistors (TIP41C and TIP42C) attached to it with replacements and the problem persists. I desoldered the sound system components and attached an external TDA2030AL soundboard but the problem persists. I soldered in a new thermistor for good measure and it solved nothing. I think it might be the power supply. I took some time and traced out the components on the board. I will have to wait for a new power supply to arrive.