W Audio PSR 15A Active Speakers
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, and noticed two fuses F3 and F4 blown as well. These are on the direct lines from the PW capacitors so no surprise there, but both fuses? Replaced the fuses with the same type and rating,and checked around for anything else that may be a problem, but nothing found, switched on, no ham but both fuses blew again. Further checks showed that one side of the fuses were short circuited, and this was also traced to the HF mixer amp TDA7253. Looks like the bulging capacitor had done more damage than we expected because several pins on the IC were also shorted to the tab. Replacing this brought the amp back to normal operation.
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, and noticed two fuses F3 and F4 blown as well. These are on the direct lines from the PW capacitors so no surprise there, but both fuses? Replaced the fuses with the same type and rating,and checked around for anything else that may be a problem, but nothing found, switched on, no ham but both fuses blew again. Further checks showed that one side of the fuses were short circuited, and this was also traced to the HF mixer amp TDA7253. Looks like the bulging capacitor had done more damage than we expected because several pins on the IC were also shorted to the tab. Replacing this brought the amp back to normal operation.
