>
>Hello All,
>
>
>
> I'm in the process of repairing an Alpha 76CA for a friend. For some reason
>he fried the plate choke (maybe out of band operation). Replaced the plate
>choke, all else visually looked good and tested good. Upon firing it up I
>noticed that I had no output although there was plate current. After close
>visual inspection, I discovered the braided staps used to connect the band
>switch to the LOAD cap was very brittle and had broken away from the variable
>cap. ( Is it possible a No-Load condition could have fried the plate choke ?)
>
not likely. My guess is that the old choke needs to be rewound with
silicone-varnish wire and checked with a dipmeter after installation. If
a resonance is found within 5 or so percent of an operating freq.,
removal of turns is indicated.
> Since it is too short to simply re-attach to the screw stud of the cap, I
>was wondering what the best type of conductor would be to replace the strap
and
>re-connect the circuit. I was planning on using a piece of 12ga. solid copper
>conductor from a piece of Romex. Anyone have a better idea?
>
Heating is common in tank circuits. . This causes expansion and
contraction stress, which leads to broken joints. One solution is to use
slightly curved conductors of thin copper ribbon at discrete points
instead of rigid conductors. . A source of copper ribbon is to cut up
plates from a kaput vacuum variable C. I prefer to solder copper ribbon
with 95% tin/5% silver solder (melts at 221 degrees C). Such solder is
much stronger, more conductive, and flows better than lead solders.
However, lead solder remnants should be removed before a joint is
resoldered with silver/tin solder
- later, Eric
Rich. Measures. Web site: www.vcnet.com/measures
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