Repairing the tuning knob of the IC-728 transceiver
transceiver that came into the lab, had a loose tuning knob. Initially
I thought it was just the screw that held the tuning knob to the shaft,
but the problem was much worse. From the usage throughout the years the
shaft of the tuning encoder had worn out and the tuning knob was loose.
The mechanical break of the knob didn't help to solve the problem.
The encoder had to be taken apart from the radio and very carefully opened. Then the old shaft had to be removed by drilling through it very carefully without damaging the white plastic or the encoder PCB with the sensitive contacts below it. The job was very delicate and if a mistake was made, the transceiver would be thrown to trash, as the encoder part is discontinued and rare to find.
thing to do, was to make a new shaft for the encoder. I did that on the
DB-200 lathe. There have been several tries, so as to achieve the
accuracy that was needed for a smooth turning of the encoder knob.
Finally the shaft was made and fitted into the encoder body. The
previous shaft was held to the plastic of the encoder by bending it
towards it. My new shaft uses a small screw and a bit of glue to keep
it secure into place.
My new shaft
is cylindrical all the way out, no need for a half-cut on it. In fact
this was better, because it allowed the tuning knob to be offset a bit
(by attaching it to the shaft at a different angle), so that it
balances the offset of the shaft due to the lathe tolerances. This
balance results in a steady knob and without any wobbling as you rotate
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