I've just run into an odd problem with a TS-850 I have on the bench.
The complaint was that the tuning knob became intermittent and then
finally quit working.

There was no problem with the rotary shaft encoder, and IC14 which the
encoder connects too was also OK. The problem was a blown circuit board
trace between CN3 (the connector from the encoder) and IC14. The traces
from CN3 to IC14 pass underneath the memory battery BA1. The battery
had started to leak, very slightly, and dropped some battery material
onto the circuit board, corroding one of the traces between CN3 and
IC14. The memory battery still worked, and everything else about the
radio worked normally. Upon normal observation, you probably would not
have noticed a problem with the battery, because the leak was on the
underside.

Just thought I'd pass along this info. The memory batteries are about
$9.50 from Kenwood or Dantona a maker of cordless phone and memory
batteries available from most electronic distributors also has them for
less. You have to remove the digital unit to replace the battery. It's
no 5 minute job, but well worth the effort to avoid a bigger problem.

73, de Rick, KN3C