elnaldo
Lunatic Member
Hello. I have a powerful chinese power amplifier and mixer, very useful in my bench, that has failed 2 times catastrophically, sparks and explosions inside, burned resistors and outputs, but fuses not blown.
I don't have the schematic, but each channel output has 2 x 2SC5200 and 2 x 2SA1943 (original toshiba bought from mouser). It has 2 fuses at the AC secondary going to the rectifier bridge, 8 A each (PCB mark is 10A) (tried smaller, 6A, but it burns after several power-on cycles, it gets red with the surge current and fails later)
The "incidents" were produced by some loud crackling noise or thump coming from preamplifiers under test, a loud BANG and the disaster started, 2 times already. I want to fix it and protect it from another event.
My 2 questions: Why a power amp could fail that way? some output transistor that can't hold some high current peak, starting a cascade fail? If so, how that high current peak is produced? The PS is +-60V
And then, how could I fuse this, to avoid the disaster again? Fuses or polyswitches at each V+ and V- rails before the output transistors, each channel separately? I don't need the full power, the amp will never play loud PA levels, it's in a small room, so I can "under" rate the fuses to be on the safe side...
Any ideas will be welcome.
Thanks!
I don't have the schematic, but each channel output has 2 x 2SC5200 and 2 x 2SA1943 (original toshiba bought from mouser). It has 2 fuses at the AC secondary going to the rectifier bridge, 8 A each (PCB mark is 10A) (tried smaller, 6A, but it burns after several power-on cycles, it gets red with the surge current and fails later)
The "incidents" were produced by some loud crackling noise or thump coming from preamplifiers under test, a loud BANG and the disaster started, 2 times already. I want to fix it and protect it from another event.
My 2 questions: Why a power amp could fail that way? some output transistor that can't hold some high current peak, starting a cascade fail? If so, how that high current peak is produced? The PS is +-60V
And then, how could I fuse this, to avoid the disaster again? Fuses or polyswitches at each V+ and V- rails before the output transistors, each channel separately? I don't need the full power, the amp will never play loud PA levels, it's in a small room, so I can "under" rate the fuses to be on the safe side...
Any ideas will be welcome.
Thanks!