12-21-2017, 02:14 PM
A couple of additional notes on this radio;
1. I reduced capacitor 13 (detector cathode) to 250pf after reading several posts on dealing with distortion. There was some improvement.
2. This radio had previously been modified with resistor 20 (input to 1st audio) having another resistor placed in parallel to it. The original was not out of spec so it had to be changing the value. Curious, I put a 1 meg pot in place and varied it. It had less distortion at values below the 500k specified, also slightly less audio. But it did seem to improve sound quality.
3. When doing the recap I found that this was a model 20 but put in the caps for 20a and moved the B+ line to the low side of the field coil.
Not back in the cabinet yet but playing very nicely on the bench with my AM transmitter set to about 30% modulation.
Rick
1. I reduced capacitor 13 (detector cathode) to 250pf after reading several posts on dealing with distortion. There was some improvement.
2. This radio had previously been modified with resistor 20 (input to 1st audio) having another resistor placed in parallel to it. The original was not out of spec so it had to be changing the value. Curious, I put a 1 meg pot in place and varied it. It had less distortion at values below the 500k specified, also slightly less audio. But it did seem to improve sound quality.
3. When doing the recap I found that this was a model 20 but put in the caps for 20a and moved the B+ line to the low side of the field coil.
Not back in the cabinet yet but playing very nicely on the bench with my AM transmitter set to about 30% modulation.
Rick
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