Hi, have a pair of these and one of them developed a hum and then the high frequency horn stopped working. The low frequency 15 inch was fine, except was was a bit woolly....

Anyway, we decided to have a look....on the power supply end of the amplifier board marked D0501PM07 V1.1 there was a very bulging smoothing cap, 6800 40v, obviously a cause of the hum. This uses the complimentary pair 2SC5198/2SA1941 for the low frequency amp and a TDA7253 for the HF mixer and other duties.

So we have stripped the board out, replaced the cap with another, same value, high voltage,...