I had some time this morning and I needed something to do, so I went ahead
and dismantled the 920. I immediately discovered that the VFO 'A' shaft
(where the knob attaches) is actually part of the optical encoder
assembly. Uh-Oh, thinks I.
I went ahead and removed the encoder from the front panel and found that,
yes, the shaft bushing was seized. Since the only options at that point
were purchase of a new optical encoder assembly -OR- further dismantling, I
chose the latter. The encoder is held together by four screws. Removal of
these screws allows you to seperate the shaft and bushing assembly from the
encoder body. The encoder is not sealed in any way and is not 'timed' so
this will not (should not) cause any functional problems.
After removing a c-clip, I was able to lightly tap the shaft out of the
bushing. The aluminum shaft was galled badly, probably due to the age of
the lubricant or possibly dust getting past the rudimentary shaft seal
Yaesu installs. A quick polishing of the shaft and inside of the bushing
with 60, then 120 emery cloth and a touch of Lubriplate had the shaft
running smooth again.
After reassembly, the knob is running like new. The entire process took
about 90 minutes, including learning time on radio dismantling. The only
tools needed are several small phillips-head screwdrivers, the proper
allen-head driver for the tuning knobs and a small pliers for removing the
concentric bushing holding the encoder to the front panel. The entire
front panel is set up to hinge forward and the display board can be moved
out of the way of the encoder by removing two screws.
Hopefully this will help someone in the future.
Jay W9RM
Keith J Morehouse
Managing Partner
Calmesa Partners G.P.
Montrose, CO
>
> Apr 10, 2012 08:45:45 AM, w9rm@calmesapartners.com wrote:
>
> The VFO 'A' tuning knob on my FT920 VHF IF radio has, after a several month
> period of noticeable stiffness, finally locked up tight. I know this was a
> failure point on other FT models of the 90's and early 2000's and am
> curious if anyone has ever had a 920 apart for the problem.
>
> I am assuming there is a bushing on the shaft that has given up and either
> galled the shaft or disintegrated. What does it take to get in there ?
>
> Jay W9RM
>
> Keith J Morehouse
> Managing Partner
> Calmesa Partners G.P.
> Montrose, CO
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>
>
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