Diagnosis

Active speaker if we turn and we turn up the volume just a buzz sound

Active speaker models:

What causes it? soon we investigate

Always we start checking the power supply in the area, it has been imagined by the time we heard the buzz. Once open active speakers seem clearly we see the charred resistor body. Apparently we did the measurement resistor is not connected to another circuit, may have been a one plug socket (socket ac transformer out is not the same as the one on the pcb) and is due to an error that has certainly (already dismantled itself).

Amplifier circuit:…

We do voltage measurements for tone control system turns out there are only 3 volts to two poles (- and), we remove the connected load is 2 pieces IC JRC4558 and we measure the voltage becomes normal again the result is 9 volts (- and). To find out which one is defective ic because there are 2 then we attach a new one and we know the results later.

IC replacement we use a small model (SMD) have run out of stock again, after we attach it again now we try to turn the active speaker. And the result is thank God everything is back to normal

IC display replacement: