Quote:
Originally Posted by ms660
Quote:
Originally Posted by Herald1360
There doesn't seem to be any AGC on the set so VR1 will be acting as a manual RF gain control- more resistance will bias back the variable mu 58s and reduce their gain. AGC would do similar by applying negative dc volts derived from the rectified carrier to the grids of the 58s. It's an odd circuit for a late thirties set!
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AGC is taken from the detector output in the original schematic and in the OP's schematic, 1meg>0.05uF>>IF>>200k>0.05uF>>RF.
Lawrence. |
So it is!
At least I wasn't wrong about VR1....
Quote:
Originally Posted by Richardgr
Hi Lawrence, thanks for your assistance!
I can see what is wrong with the bias for the 2A3, I think. It is a sort of back-bias arrangement, and I should have a polarised capacitor there. Currently I have a 1uF MKP.
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It matters not here whether the 1uF is polarised or not. The MKP is fine and could be used either way round, a polarised capacitor would have to be the right way round!