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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 21st Aug 2019, 11:48 am   #1
ms660
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Default Circuit Analysis?

Out of interest, ideas on this one please....

EBF80's D2?

AM detector load path?

https://nvhrbiblio.nl/schema/Grundig_80U.pdf

Lawrence.
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Old 21st Aug 2019, 12:59 pm   #2
kalee20
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Default Re: Circuit Analysis?

I wondered if it was a clamp diode, in a delayed-AVC system. But I can't see a high-value resistor trying to take the AVC line positive (until overcome by a strong signal's negative rectified carrier). So abandoned this idea.

I think it's just there to give a bit of negative zero-signal bias to the AVC line by contact potential.
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Old 21st Aug 2019, 1:09 pm   #3
ms660
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Default Re: Circuit Analysis?

Replies in bold bold:

Quote:
Originally Posted by kalee20 View Post
I wondered if it was a clamp diode, in a delayed-AVC system. But I can't see a high-value resistor trying to take the AVC line positive (until overcome by a strong signal's negative rectified carrier). So abandoned this idea.

Yes....me too

I think it's just there to give a bit of negative zero-signal bias to the AVC line by contact potential.

I think that could be it
What about the AM detectors diode load path, is it like that to save on switch contacts or is there something else going on...

Lawrence.
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Old 22nd Aug 2019, 6:46 pm   #4
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Default Re: Circuit Analysis?

Is the AM load through the ratio det circuit, it does seem it saves switch contacts?
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Old 22nd Aug 2019, 7:05 pm   #5
ms660
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Default Re: Circuit Analysis?

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Is the AM load through the ratio det circuit, it does seem it saves switch contacts?
I'm not absolutely sure Frank, there's a debate about this on the GVR forum.

The only description of the other diode I can find so far in a similar AGC setup is in the Trader sheet for the KB GR15 where it appears to be a clamp diode to prevent the AGC line going +ve, as to whether that's its correct function is a case of who knows at the moment until I can find some other reference that fits the bill.

All theories welcome..

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