[Kenwood] Strange TS940 problem

[Martin Sole]

I have been fixing a friends TS940. It was very insensitive and had a
couple of intermittent faults which I think are fixed. One problem
however remains. I have never seen this before on any of the half dozen
or so 940's that I have fixed and am a little baffled so any ideas
appreciated.

What happens is that with a steady signal coming from my comm test set
giving a reading of say S8, audio is heard as expected. Now going to
transmit, don't worry the comm test set does both and can handle the
power, it doesn't actually matter what mode or if there is any power, or
if you are in a segment that cannot transmit, but providing you remain
keyed for more than about 5 to 7 seconds, on release of the PTT the S
meter initially will rise to about 5 or 6 then after a second or so it
wobbles and settles back at S8. At the same time a raspy edge can be
heard on the audio.

It sounds to me almost as if a loop somewhere is on the edge of
unlocking but I can't recall anything that changes, frequency wise, when
going from transmit to receive. Does this sound like a PLL alignment
problem? I've never been any good at replicating Kenwood's graphs in the
service manual.

All ideas appreciated.

Regards
Martin, HS0ZED