"Jeffrey Landgraf" wrote in
:

Gentlemen,

My Yamaha P2100 stereo amplifier has "crackling" and hissing on a
single channel. It started out intermitant and would disapear (for
awhile) when the amp was turned off and then back on immediatley. The
audio from that channel is very thin sounding as well. I've replaced
all the electrolytic caps awhile back and the problem remains. I'm an
experienced board level trouble shooter but I'm trying to cut the time
for diagnosis to a minimum. In my experience "thin" is often dried out
caps but this amp design does not use many electrolytics ( and they've
been replaced!). I've not fixed an amp with crackling and hissing.
Any ideas on which components would likely cause these symptoms?

Thanks,
Jeff


You need to trace the noise back from the output with an oscilloscope.
This can be tedious without a schematic. Go back stage by stage. Does the
power amp have discrete transistors or a big hybrid block? Email me if
you like.

Tim