[Milsurplus] Somewhat deaf BC-312

[Ian Wilson]

I have a radio that I am fairly sure was originally a BC-312 (actually, I
thought it was
a BC-342 but have been doing some homework). It has a number of
modifications,
one of which has mounted an S-meter over the nameplate <g>.
There is no crystal filter (it has a dial light control), and there is a
very well-constructed power supply in place of the original.

About a week ago, I brought it up gently on a Variac. Everything worked, no
smoke,
so have been running it normally since then.

Initially it received both AM and CW with good sensitivity, although the
audio was rather low (using a good pair of high-Z headphones). It was
pulling in 10MHz WWV
fine on a few feet of 'antenna'.

Over the past couple of days the audio level has faded more, and I can no
longer
hear AM signals. With the BFO on, I can hear CW signals, and can tune AM
signals by zero-beating the carrier. But AM seems to have gone.

What's a likely cause of this? Seems to me that the problem must lie with
one or
more RF stages or perhaps the AGC line (although the gain control in both
AVC
and MVC settings appears to be working still). Am going to pull the RF tubes
and
see how they appear on a tube tester.

Thanks for any suggestions,

--ian K3IMW
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