hismasters: 1121: Repairing Volume Control

The volume control spindle fell out. In this case not due to pulling the knob off as the knobs come off easily on the HMV 1121. These old long shaft high value logarithmic potentiometers (log pots) with a mains switch are hard to get so can it be repaired?

 

Well, the first stages are to take it out of the radio (making a note of where the wires go) and then carefully prise up the tabs holding on the cover & switch.

It seems like the steel shaft is forced into an interference fit alloy splined socket rather than the more common rivited construction. The start of the track looks badly worn, the solutions are silver PCB repair paint or to bend the two wipers away from previously used part of track or else the volume won't fully turn down.

Check no parts are broken and clean / degrease (alloy debris removed from stee shaft). The paxolin base with wipers (to left near shaft) is first "super glued" to the Alloy back plate (to right of shaft).

The shaft is held in vise and super glue put on splines, Then a single strong blow using a pin or bolt:

After a single hard thump!

Then test the "pot" with a meter.
 

Make sure the on/off switch works on both poles (may need switch cleaner and operated a few times) and put it in the "on" position.

Switch in "on" position

 

Then if everything is working insert into panel but solder wires before adding the nut.

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