Today update
replaced power caps with matched 15,000 uf ones
replaced Zobel resistors both channels
After about 10-15 minuets under light load ( warming things up)
left channel running only 5 volts output
.132 mv at 1.2k input
N+THD .08%
initial warm Bias .3mv at 75volt both channels
8ohm load connected on driven left channel only (the problem child )
rail at 75v with 150v across caps ( low z setting)
no heat in heatsinks (80-90'F)
sitting and sipping a cup of tea and as I watch the unit do the following observation
Slight voltage drop in room ( slight loading sound)
Suddenly both vu meters rise( only one driven) to about -10 db on meters then driven left chann neg Rail fuse blows (only have 4 amp at this time as s little caution and last time the positive fuse blew)
rail voltage steady at 150v
blown driven Chan had minimal bias mv on left chann with right channel still at .310mv after fuse blew
turned off and now scratching my head
question what caused both channels to show high output on meters
did not have scope in sight when happened.
Something suddenly drove both channel with only one input connected
left channel is one blowing fuses wether under load or not.
Rise in output to excead the 4 amp fuse on loaded channel is obviously the case for fuse going out this time
unloaded channel into no load did not pass enough current to blow fuses yet this channel was suddenly driven
the indecent was not fast as it took about one second to rise and blow
are we any wiser ??
ideas anyone