05-01-2014, 01:36 AM
I've been working on this set for a few days now. I don't have the service packet from Chuck yet, but the radio is essentially the same as the schematic from the Code 121-122 schematic.
I finally have the radio stable enough that all three bands are good, except above 19 MHz, where the LO seems to die. I'm going to order a new 6A8 to try to take care of that.
Also, I now have enough gain to get some noise floor on all bands.
Now here's the fun part(s):
With no antenna attached, I get signals on all bands, but at lower volume levels.
With my random longwire attached, the stations get very much louder. The AGC is developing good negative voltages to the grids of the 6A8 and 6K7. Unfortunately, that voltage does not seem to actually DO anything to regulate the input signal.
Add to this that when the longwire is connected, I have input overload across the BCB to the extent that there are spurs all across the dial.
The antenna coils all seem to be fine. The primaries are all continuous and the secondaries are continuous and also tune properly.
The 6A8 cathode resistor measures 106 ohms, whereas it should be 100 ohms. Well within tolerance.
Any ideas? This one really has me scratching my head. Other than the total lack of AGC action (despite a good range of voltages being developed: -1.5 to -13.5V), the set seems to perform quite well.
I finally have the radio stable enough that all three bands are good, except above 19 MHz, where the LO seems to die. I'm going to order a new 6A8 to try to take care of that.
Also, I now have enough gain to get some noise floor on all bands.
Now here's the fun part(s):
With no antenna attached, I get signals on all bands, but at lower volume levels.
With my random longwire attached, the stations get very much louder. The AGC is developing good negative voltages to the grids of the 6A8 and 6K7. Unfortunately, that voltage does not seem to actually DO anything to regulate the input signal.
Add to this that when the longwire is connected, I have input overload across the BCB to the extent that there are spurs all across the dial.
The antenna coils all seem to be fine. The primaries are all continuous and the secondaries are continuous and also tune properly.
The 6A8 cathode resistor measures 106 ohms, whereas it should be 100 ohms. Well within tolerance.
Any ideas? This one really has me scratching my head. Other than the total lack of AGC action (despite a good range of voltages being developed: -1.5 to -13.5V), the set seems to perform quite well.
