I bet most of you have had this sort of repair to do.
The radio came with the cir-clip and plastic lugs still firmly attached to the tuning cap spindle but separated from the actual tuning knob.
The first job was to get the old broken part off, there was no way I could pull it off the spindle from the front by the rotating dial because that was already showing signs of cracking. But luckily I could just get a screwdriver blade in behind it and levering against the body of the tuning cap managed to prise it off.
I decided that the original cir-clip spring was too thick to allow enough epoxy to be moulded around the centre of the knob. So I made a new collar from thin tin plate shaped into a circle, I soldered the overlap to strengthen it.
I could not find my piece of brass rod which I had used on other occasions for this type of repair. But an old variable resistor with a nylon spindle seemed to be the right size. Luckily there was just enough plastic left in the centre of the knob for the flat on the pots spindle to locate and stand up.
I fitted my new collar to the knob by heating it with a soldering iron enough to be able to press it down into the plastic so it was held nicely in the centre, (well as close to centre as I could tell)
Next I waxed the end of the pots spindle and covered the end with epoxy filler. I located it in the knob, then tamped the filler down into the collar until it slowly oozed through the remains of the slots in the centre of the knob. I drizzled in a little more epoxy filler being careful to not trap air bubbles.
It took more than 24 hours for the epoxy to set enough to enable me to trim off the surplus and slowly pull the potentiometer spindle free, it slid out with a faint pop.
The new collar on the knob fitted perfectly over the tuning cap spindle, with a little stiff wax smeared around the spindle it was a nice tight push fit, the wax ensured that if would not slide of with out help. I found that the repaired tuning knob runs nice and true.
I gave the radio cabinet a good clean and polish, I decided to not over polish the brass names and fittings but to leave the patina gained over the years.
Mike
ps.
The radio works but it is quiet and lots of interference with the stations on MW. LW is a simple preset and works better, it was still tuned to R4.. I have decided to not recondition the electronics to improve it as I will not be using the radio as it requires 2 6v batteries which I dont intend to make, and I cant find a decent circuit with voltages marked.
The radio came with the cir-clip and plastic lugs still firmly attached to the tuning cap spindle but separated from the actual tuning knob.
The first job was to get the old broken part off, there was no way I could pull it off the spindle from the front by the rotating dial because that was already showing signs of cracking. But luckily I could just get a screwdriver blade in behind it and levering against the body of the tuning cap managed to prise it off.
I decided that the original cir-clip spring was too thick to allow enough epoxy to be moulded around the centre of the knob. So I made a new collar from thin tin plate shaped into a circle, I soldered the overlap to strengthen it.
I could not find my piece of brass rod which I had used on other occasions for this type of repair. But an old variable resistor with a nylon spindle seemed to be the right size. Luckily there was just enough plastic left in the centre of the knob for the flat on the pots spindle to locate and stand up.
I fitted my new collar to the knob by heating it with a soldering iron enough to be able to press it down into the plastic so it was held nicely in the centre, (well as close to centre as I could tell)
Next I waxed the end of the pots spindle and covered the end with epoxy filler. I located it in the knob, then tamped the filler down into the collar until it slowly oozed through the remains of the slots in the centre of the knob. I drizzled in a little more epoxy filler being careful to not trap air bubbles.
It took more than 24 hours for the epoxy to set enough to enable me to trim off the surplus and slowly pull the potentiometer spindle free, it slid out with a faint pop.
The new collar on the knob fitted perfectly over the tuning cap spindle, with a little stiff wax smeared around the spindle it was a nice tight push fit, the wax ensured that if would not slide of with out help. I found that the repaired tuning knob runs nice and true.
I gave the radio cabinet a good clean and polish, I decided to not over polish the brass names and fittings but to leave the patina gained over the years.
Mike
ps.
The radio works but it is quiet and lots of interference with the stations on MW. LW is a simple preset and works better, it was still tuned to R4.. I have decided to not recondition the electronics to improve it as I will not be using the radio as it requires 2 6v batteries which I dont intend to make, and I cant find a decent circuit with voltages marked.
