National NC-44/45 receiver AGC woes.
Well I got the NC receiver going except for one important thing!
The AGC makes NO sense at all.
I've tried it with the original 6L7 tubes and 6K7's with G3 connected to cathode
but I seem to get a VERY low DC control voltage output from the AGC system and the
detector is being overloaded on BC stations.
Now even with 1 IF stage I would expect to be getting about -5 volts on the AGC line on tune.
But although everything tunes up OK (IF set to 450 kHz) we only get about -2 volts.
Obviously this is NOT enough to drop the gain of the controlled stages enough.
I have tried experimenting with different AGC arrangements even using a diode voltage
doubler but to no avail.
Anyone else ever come across a problem like this? I've been in electronics since 1950,
but this is a new one on me. BTW I checked up on the 6L7 and it can give some very odd
results, hence the tube change, but with no result.