07-01-2021, 09:39 AM
I'm guessing it's a B, no identifying labels on the chassis my customer just gave me the chassis and speaker to restore.
I was looking for a schematic that matches the wiring on this chassis. This one has the later(?) detector circuit and volume control
and has the second AVC line to control the suppressor grids of the RF and 1st IF tube, but they also connect to a
fixed -2.4V tap on the divider resistor. Was this another change in the design? I removed the fixed -2.4V connection and the sensitivity got
better (recovers good audio down to 5uV @ 18MHz) and appears to help quite a bit on very high RF inputs, tested up to 5,000uV.
Chuck
I was looking for a schematic that matches the wiring on this chassis. This one has the later(?) detector circuit and volume control
and has the second AVC line to control the suppressor grids of the RF and 1st IF tube, but they also connect to a
fixed -2.4V tap on the divider resistor. Was this another change in the design? I removed the fixed -2.4V connection and the sensitivity got
better (recovers good audio down to 5uV @ 18MHz) and appears to help quite a bit on very high RF inputs, tested up to 5,000uV.
Chuck
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