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In the picture is an audio power amp from about 1978 by AB Systems, Inc.
I have replaced all the output devices with modern ones (some of the old ones had failed, but nothing else) and I get a little oscillation near clipping on the positive peaks of a signal. This occurs with or without a dummy load connected.
I looked at the diagram and realised that it has many capacitors that I wasn't used to seeing in audio amps, arrowed in red.
Any suggestions as to what they all do and why they are there, or is it just a bit of a mess?
I can see the 47pF is the so-called Miller capacitance, but the others I have not seen before.
The 0.05 uF caps around the V-I protection transistors are in the wrong place, but removing them didn't help.
I can't see D17 and D18 being much help, either.
Any thoughts?
I have replaced all the output devices with modern ones (some of the old ones had failed, but nothing else) and I get a little oscillation near clipping on the positive peaks of a signal. This occurs with or without a dummy load connected.
I looked at the diagram and realised that it has many capacitors that I wasn't used to seeing in audio amps, arrowed in red.
Any suggestions as to what they all do and why they are there, or is it just a bit of a mess?
I can see the 47pF is the so-called Miller capacitance, but the others I have not seen before.
The 0.05 uF caps around the V-I protection transistors are in the wrong place, but removing them didn't help.
I can't see D17 and D18 being much help, either.
Any thoughts?
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