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It is currently 06 Jul 2020, 17:26

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PostPosted: 20 Jun 2020, 05:31 
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Joined: 01 Jun 2013, 09:05
Posts: 963
Hello,

I am looking for someone to give ideas on the operation of some resistors on the old Mozart circuit.
I have a few ideas about this circuit but I would like opinions on, what the resistor do and why did they create this resistor configuration.

R23 - R24 - and R18 what is happening in the circuit diagram.
I.e. I'm looking for something like R23 does this etc.

Looking at R23 and R18 as an example.

Answers on a postcard to :D

Regards
M. Gregg


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PostPosted: 20 Jun 2020, 05:38 
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OK so C21 is part of a feedback network.

So what's going on and why?

The only thing I can think of at this point is that feeding the cathode resistor from the B+ rail moves the operating point of the tube by lifting the voltage on the cathode. But that is unusual and with it being something like 22meg times 2 seems a bit nuts.

I have seen this kind of thing with LED cathode bias to push the operating point of the LED's into a more linear condition but there are no LED's.

Any thoughts?

Regards
M. Gregg

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PostPosted: 20 Jun 2020, 10:01 
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Hi, Odd. It appears that C21 is an electrolytic and this might insure it does not get reverse voltages. The resistor values does seen rather high for this though.

Good listening
Bruce

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