Tom, you mentioned having another supply. Hook that one up for a while to
see if the problem appears again. If so, its not the same supply. Then
swap out each jumper switch and tuner in the same way.
I don't know anything about the tentec tuner.
I have an MFJ 989 with a big roller inductor.
Every few years I have to clean the roller and the shaft it sits on.
Lots of contact cleaner for the job.
H T Kaufman MSW LCSW
Adaptive Technology Instructor