Hello,
I'm looking to repair my Marantz PM6002 amplifier, symptoms are one channel is intermittent, mainly silence, some noise and sometimes works fine.
I have a service manual for the amp and it looks like the signal flow is input sockets, into a mux (LC78212) for source select, followed by a unity gain buffer, volume pot, tone control, and then amplifier.
The symptoms persist wherever the pot is in the range, and happens both with the tone control switched in and out, it also persists on all the inputs which rules out the input mux (there are two, depending on which input is used.)
There are a bunch of opamps, and of course the amplifier, but my current suspicion is the muting circuit, I've attached a transcription of it for one channel (CE connections are as shown in service manual.) Mute is driven from a microcontroller and is 0/5 V.
Does this sound like a resonable diagnosis, and is this a common failure mode for muting transistors?
Thanks!
I'm looking to repair my Marantz PM6002 amplifier, symptoms are one channel is intermittent, mainly silence, some noise and sometimes works fine.
I have a service manual for the amp and it looks like the signal flow is input sockets, into a mux (LC78212) for source select, followed by a unity gain buffer, volume pot, tone control, and then amplifier.
The symptoms persist wherever the pot is in the range, and happens both with the tone control switched in and out, it also persists on all the inputs which rules out the input mux (there are two, depending on which input is used.)
There are a bunch of opamps, and of course the amplifier, but my current suspicion is the muting circuit, I've attached a transcription of it for one channel (CE connections are as shown in service manual.) Mute is driven from a microcontroller and is 0/5 V.
Does this sound like a resonable diagnosis, and is this a common failure mode for muting transistors?
Thanks!
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Use a signal generator and scope, to trace the signal and control path through the amplifier channel.
There's no useful way to guess where the fault is located.
There's no useful way to guess where the fault is located.
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