|[AMRadio] Small variable cap repair|
CL in NC
mjcal77 at yahoo.com
Wed Oct 23 16:42:20 EDT 2013
This may or may not be general knowledge, but the small APC style variable caps we have in a lot of vintage gear are easily repairable if the rotor has shorted to the stator do to the solder joint failing on the rotor shaft after 50+ years. A few years ago when my trusty GE ProgLine failed due to a HV short in the TX when a cap failed, this repair brought it back to life, and I just did the same for a buddys HF XMTR with a similar failure. These caps usually mount with 2 screws and have a screwdriver adjust shaft that also has a hex shaped fitting on the shaft. These caps fail at the junction of this hex fitting and the shaft, and this is all that is holding the shaft in the capacitor and maintaining the rotor/stator spacing. If you put the cap in a vise, one jaw pushing the rotor shaft, the other, utilizing spacers in contact with the metal mounting studs, enough spacers so as not to have the rotor in compression against the other jaw, you can
carefully close the vise to center the rotor/stator, and solder the hex fitting back on, or do as I have done, drill a small hole through the hex and shaft and drive in a piece of copper wire then solder the assembly. Make sure this fitting is against the bushing passing though the ceramic body of the cap before securing it.
I thought this was a pretty good Hint and Kink for QST when I first tried it, but they didn't, oh well, my writing career dashed.
Charlie, W4MEC in NC
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