07-03-2024, 12:40 PM
One can apply this to most any RF/IFoscilator coil:
If the resistance given is any more than 10% high using an analog ohmmeter then there is corrosion present and some of the turns have been etched. Often seen as tiny green spots. Such a coil may still work...
Coils that have a layer separated with what appears to be plastic, it is actually celluloid, are always suspect. In moisture/time celluloid breakdown and creates an acid. Thus etching the turns despite the enamel..
The coil will either have to be replaced or re-wound.
To re-wind, using solvent and or heat remove all the surface wax. The start/finish of the turns can be found.
I suggest creating a diagram of the coil so all notes of how it is wound are present on the diagram.. Measure the O.D. of the magnet wires and refer to a chart to determine what size magnet wire to use. Do NOT change the wire size or the number/direction of the turns.
>>> If a coil is rewound exactly as it was, it will work with very little or no alignment required. Use magnification, count the turns. Then, unwind, counting turns a second time
Clean the form, then dip in melted bees wax and let sit for a few minutes. then remove the form, it will have a wax film on it which will aid greatly in the rewind. Follow the diagram and rewind. Kapton tape can replace the rotting celluloid liner. Coat the surface of the tape or dip in wax to make the form sticky again. Wind the top layer. Dip the entire coil in bees wax and let sit, when most bubbles have gone extract from wax and let cool. The, dip very quickly to make thick film of wax, coil is now ready to back into radio.
Use only clean bees-wax not paraffin or a candle blend. Paraffin is slippery not sticky... If there are any tags of black adhesive holding the magnet wire, that, is a production wax that melts at a higher temperature. generally that black wax does not have to be replicated as one is hand winding.
The advantage of the wax and the diagram is one can take a break from the winding and the coils will not slip off and the the process not forgotten as it is on paper.
GL
Chas
If the resistance given is any more than 10% high using an analog ohmmeter then there is corrosion present and some of the turns have been etched. Often seen as tiny green spots. Such a coil may still work...
Coils that have a layer separated with what appears to be plastic, it is actually celluloid, are always suspect. In moisture/time celluloid breakdown and creates an acid. Thus etching the turns despite the enamel..
The coil will either have to be replaced or re-wound.
To re-wind, using solvent and or heat remove all the surface wax. The start/finish of the turns can be found.
I suggest creating a diagram of the coil so all notes of how it is wound are present on the diagram.. Measure the O.D. of the magnet wires and refer to a chart to determine what size magnet wire to use. Do NOT change the wire size or the number/direction of the turns.
>>> If a coil is rewound exactly as it was, it will work with very little or no alignment required. Use magnification, count the turns. Then, unwind, counting turns a second time
Clean the form, then dip in melted bees wax and let sit for a few minutes. then remove the form, it will have a wax film on it which will aid greatly in the rewind. Follow the diagram and rewind. Kapton tape can replace the rotting celluloid liner. Coat the surface of the tape or dip in wax to make the form sticky again. Wind the top layer. Dip the entire coil in bees wax and let sit, when most bubbles have gone extract from wax and let cool. The, dip very quickly to make thick film of wax, coil is now ready to back into radio.
Use only clean bees-wax not paraffin or a candle blend. Paraffin is slippery not sticky... If there are any tags of black adhesive holding the magnet wire, that, is a production wax that melts at a higher temperature. generally that black wax does not have to be replicated as one is hand winding.
The advantage of the wax and the diagram is one can take a break from the winding and the coils will not slip off and the the process not forgotten as it is on paper.
GL
Chas
Pliny the younger
“nihil novum nihil varium nihil quod non semel spectasse sufficiat”
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