[Boatanchors] Backlash in a National capacitor

[Dave Harmon]

Ian...
I had the same trouble with a HRO 50T-1 and the backlash was noticeable and
really bad on general coverage.
The backlash was causing the smallest movement of the cap plates...so small
I could just barely see it....but it was enough to mess it up.
If I remember correctly....I had to adjust each far end of the shaft to take
out the play.
I think there is an adjustment intended for this on the right
side....perhaps both sides...don't remember for sure.


Dave Harmon
K6XYZ[at]sbcglobal[dot]net
Sperry, Ok.


-----Original Message-----
From: boatanchors-bounces at mailman.qth.net
[mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Ian Wilson
Sent: Wednesday, September 19, 2012 4:56 PM
To: boatanchors at mailman.qth.net
Subject: [Boatanchors] Backlash in a National capacitor

I have a National 4-gang HRO-type variable capacitor here. It has noticeable
backlash.
Removing the top of the gearbox and looking at the two large driven gears, I
can see that when the direction of rotation changes, there is a small dead
zone as the two gears are pulled into alignment.

Presumably this is caused either by the springs losing tension (about which
I can't do much), or by excessive drag on the shaft that rotates the
capacitor rotors. Assuming that the problem is drag, how should I
adjust/lubricate which bearings to lessen this?

73, ian K3IMW
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