Power amplifier , power supply surge when suddenly switch on and off main supply

In my stereo power amplifier 100 watt each, using 2sc5200 and 2sa1943 class AB amplifier, when i suddenly switch off the amplifier then suddenly large amount of voltage ripple occur in my speaker, i'm not using speak protection in this amplifier. But the thing is that my another amplifier using same transistors works well and didn't give any spikes when i turned off it. What could be the problem in my amplifier. Is that the fault of Power supply unit ?

by Abhi1326
June 13, 2020

If you have access to the circuit, check the capacitors, the electrolytic ones. If you see one with its top, generally flat, making a dome, a little bit like a half sphere, that is a dead capacitor. Replace it with another one with the same capacitance, same or better voltage rating, same polarity. "Tag" the new cap. in parallel with the dead one, and test for the problem. If the problem is gone, well, weld the new cap in place, and remove the old one (that assumes that you have an easy access to the leads getting out of the old cap, could be on the reverse side of the PCB). Also, not the voltage rating, if it is 50V or higher, be sure to discharge it properly, otherwise, it can be deadly. Oh, and better to use a quality capacitor as replacement, not a no-name, or it can be half dead already, even if new, out of the box, never used. Some just age faster than battery, even doing nothing other than sitting on the shelves.

by vanderghast
June 15, 2020
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