I wondered about that myself. Looking at the schematic, I do see a couple of
electrolytic coupling caps that can be causing the problem. Since Tx audio
is there for the first few seconds, this tells me that it is a Tx keyed
stage that has the problem. I am going to have to trace the Tx enable line
to see which stages are being keyed in Tx mode only.
I am looking at the block diagram, and it appears that either TR27, the PA
switch or TR21, the AF switch might be causing the problem. There is also a
feedback network that starts back from TR34, the ALC amp. This feeds a
couple of other stages caled AMC amps, that appear to go through a summing
network into TR23, the Mike amp.
Since the Tx audio problem affects both AM and SSB modes, it has to be in a
keyed stage that is common to both modes.
The nice thing about this radio is that no mods appear tohave been
done.............even the clarifier control has not been "married" to the Tx
mode. This one is worth fixing........the only problem is getting at all of
the wiring. Much of it is hidden behind a shield plate at the front panel.
It could be something as simple as a cold solder joint, but that might just
be wishfull thinking!

Pete

"John Doe" wrote in message
...
Sounds like a RESISTOR is changing value causing the bias to change on the
input preamp.

"Pete KE9OA" wrote in message
. ..
Another eBay special that "worked perfectly". It doesn't matter if I put
in an external audio source from an audio oscillator or a microphone.
I've tried three good microphones, and have the same problem. When I
first key the mic, Tx audio is fine, but it quickly, almost abruptly
fades after about 2 seconds. Has anybody seen this problem?

Pete