[Boatanchors] Roller inductor refurbishment

[Ian Wilson]

I have been refurbishing a roller inductor, provenance unknown,
scavenged from a particularly nasty homebrew antenna tuner.

The roller is 6" long, 2" dia, made ALSIMAG ceramic. Total
inductance about 30uH.

Originally everything was very stiff and there was a noticeable
wobble as I turned the spindle. I was able to improve this a lot
by adjusting the stub axles which are held in place by paxolin(?)
pieces that are fixed to the roller inductor with nuts/bolts.

The variable tap is a sliding brass piece with a shaped runner
(not a roller). There are springs that keeps the runner in contact
with the inductor wire.

This is working much better than originally, but there is a small
amount of residual wobble. An inductance meter reveals that the
slider is losing contact when the wire is furthest from the roller.

I don't know whether the loss of contact is where the slider meets
the wire or between the moving parts of the slider (sorry; I know
that a picture would help here).

The end pieces are made of some ceramic, so no adjustment
is possible there.

Any suggestions for determining where the loss of contact is
and/or fixing this?

73, ian K3IMW