[Milsurplus] BC-779 Update

[Carole White-Connor]

Thank you for your responses! It's amazing to be able to call upon the
collective experience of guys like you, all of whom have been under the hood
of a BC-779. (I'm also spoiled. Al Klase sold be a civlian version of this set
that performs unbelievably well!).

New Observations:

1. My problem is overload, not distortion. When I put it in manual mode and
turn the sensitivity down, I get clear, good audio.

2. The filament voltages are about 5.2V, instead of 6.3. There are two 4-ohm
filament dropping resistors. Each reads about 2.5 ohms. Do you think these
resistors might be causing the low filament voltage? While the power supply is
home brew, the transformer does have a 6.3v (5A) secondary. Tomorrow, I'll
take the terminal strip off the back and measure the filament output from the
power supply without the receiver attached.

3. As I was testing voltages, I had the radio on AVC and both sensitivity and
audio set at zero. Nevertheless, I still got a weak but audible station
through the speaker. Do you think this points to the sensitivity pot or audio
pot as the problem? I haven't had the front panel off so I haven't tested them
yet. Do you think this might have something to do with my issues?

Old Issues

1. I subbed in 6F6s for the 6K6s that were there. No change.

2. I double-checked the AVC chain. I had previously replaced all the caps in
the chain.(The manual contains a nice schematic of the AVC chain). I thought I
had gotten all the out-of-spec resistors but I found a fried 2K resistor in
the AVC can that I had overlooked. It read about 300 ohms. I changed it and
got some improvement with the overload.

3. I did replace C-13. It looks like it had been previously replaced. It was
an Erie Ceramicon of the wrong value (95 pf, not 92). I put in a 82 pf
silver-mica cap and noted some improvement in sensitivity. However, it was not
causing the overload.

As always, thanks. This is a beautiful set and I want to get it playing right.

Joe Connor
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