I've got another of these 650's here. I'm having issues with the bias/feedback circuit for the the "low frequency" channels (orange/black & yellow brown)
This amp has previously been worked on before and D41D8 + D40D8 have been replaced with 2n6491 + 2n6488 (installed by shifting the transistor over one slot and using a jumper for the emitter)
There were a lot of issues with these two channels, and I have already replaced the majority of the components for them. ie, output fets, drivers biasing pots, several resistors, both op amps, and all zeners.
I'm getting ~ -1.5v dc on the outputs for these two channels and I just can't seem to track it down. This is with the bias pot at minimum (fully counter clockwise), but I can actually get rid of the dc voltage on the outputs by adjusting the bias
The problem with this however, is that the output fets are heating up excessively. I'm obviously missing something, but like I've said I just can't track it down. I'm wondering if the 2n6491 + 2n6488 are causing more problems than not?
Thanks in advance
This amp has previously been worked on before and D41D8 + D40D8 have been replaced with 2n6491 + 2n6488 (installed by shifting the transistor over one slot and using a jumper for the emitter)
There were a lot of issues with these two channels, and I have already replaced the majority of the components for them. ie, output fets, drivers biasing pots, several resistors, both op amps, and all zeners.
I'm getting ~ -1.5v dc on the outputs for these two channels and I just can't seem to track it down. This is with the bias pot at minimum (fully counter clockwise), but I can actually get rid of the dc voltage on the outputs by adjusting the bias
Thanks in advance
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