I just got my 820 out of retirement after at least 14 years. It has the
digital display and IF output on the back but is labeled TS-820, not TS-820S
and I'm not sure why... anyway when I turned it on the display came up
garbage ( 99__.9) while using both the internal and external VFOs. Finally
(after 20 minutes) the frequency appeared correct but would jump around
while tuning. By the noise level I could tell that it was actually changing
frequency, and not a display problem. More time passed and it seemed to be
correcting itself even more but while tuning it would go from (for example)
3599 to 3700 skipping the 3600-3699 completely. I'm not sure that this was a
frequency error or readout error but since the noise level did not change I
am thinking it was a freq. display problem. I took off the top and bottom
covers and tightened all the available screws in and around the VFO area as
well as circuit boards. More time passed and finally, after maybe 2 hours
everything was fine.

I then turned it off, went to a meeting and when I returned and again turned
the rig on the instability started again. It wasn't as radical as before but
like before it seemed to correct itself after about 45 minutes. After
another 15 minutes I tuned it up and the transmitter worked fine as did the
receiver.

I know this is an old radio but I love it and can load it into a barbed wire
fence if I want to and it doesn't mind. I have the external VFO, station
monitor, and external speaker and it has always worked flawlessly.

If anyone has a suggestion I sure would appreciate it.
73,
Ken