Got a Fender Frontman 212R that has a strange problem, once in a while it will chop off the bottom half of the output wave,
common problem, about 300 complaints on the internet but nobody has come up with the answer,
the amp will latch up in this failure mode and then start working again.
touching a voltmeter lead to the cathode of D4 makes the amp work right again.
messes with a new TL072, messed with the feedback circuit, took some good and bad voltage measurements,
bad Veb volts shown on pic,
the diff pair works off the +/- 42 volt rails which have a bit of dirt.
i was thinking of putting in a resistor / cap filter section on the rails to the diff pair,
maybe bad filter caps?
do you think this will help?
Thanks!
full schematic attached as pdf
common problem, about 300 complaints on the internet but nobody has come up with the answer,
the amp will latch up in this failure mode and then start working again.
touching a voltmeter lead to the cathode of D4 makes the amp work right again.
messes with a new TL072, messed with the feedback circuit, took some good and bad voltage measurements,
bad Veb volts shown on pic,
the diff pair works off the +/- 42 volt rails which have a bit of dirt.
i was thinking of putting in a resistor / cap filter section on the rails to the diff pair,
maybe bad filter caps?
do you think this will help?
Thanks!
full schematic attached as pdf
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