[R-390] capacitor analysis

[John Saeger]

Michael Melland wrote:

> Mine has had a pesky AGC problem which was very intermitant.  On strong
> local stations all of a sudden I'd loose AGC action.... voltage would drop
> on the AGC buss from -9vdc to -4-6vdc and heavy distortion until the gain
> was backed off.  Then it would stay like this for a while and suddenly
> return to normal.
>
> Finally tracked down the problem Friday to a bad 4 Kc filter that when it
> got heated up would short internally and screw-up the AGC line.  When it
> cooled a bit it was ok......

I haven't measured the voltage on the AGC buss, but this is almost exactly
what mine is doing.  I get a drop in carrier level with a lot of distortion,
and a sudden return to normal.  On strong local stations.  But it doesn't
seem to depend on which filter I have switched in.

And thanks to everyone who has posted on the capacitor subject.  Interesting
food for thought.

John