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Short wire on tuning capacitor on 41-250 and 41-280 - Printable Version

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Short wire on tuning capacitor on 41-250 and 41-280 - Raleigh - 06-04-2007

On both of my 1941 Philcos there is a short stub of stiff, insulated wire soldered at one end to a terminal on the top of the variable capacitor. The other end is just cut off.

On one of the radios the wire is about 2.5 inch long, and is soldered to the teminal on the capacitor on the left. It curves through the terminal on the other variable cap (kind of an "S" shape) but doesn't make electrical contact with that terminal because of the insulation.

On the other radio, the wire is about 1.5 inch and runs horizontally but does not touch the other terminal. There are traces of solder on the terminal that doesn't have the wire on it.

I don't see anything on the schematic. Anyone have any idea what that wire is for or what it may have been connected to at one time?

- rghines1 - 06-04-2007

Think these are so called gimmick capacitors you are describing. They only connect at one end and are only a few picofarads of capacitance. Zenith did this on some of their radios. A small amount of the oscillator signal is coupled back to the RF input lead of the mixer stage. It was negative feedback that was important at shortwave frequencies.

Richard

- Ron Ramirez - 06-04-2007

Richard is correct in that this is known as a "gimmick" capacitor.

Replace the insulation on that wire, and then put it back the same way it was. Otherwise the radio will not function properly. If you do not replace that rubber insulation, it will crumble and short over time.

- Raleigh - 06-05-2007

I have wondered what a "gimmick" was. I ran across the term in a book on radio repair, but it wasn't explained.

One last question. Was the gimmick trimmed and routed for each radio or was it just cut to a predetermined length and routed according to a print? The reason I ask is that I already replaced them both with new wire, cut to length and routed as in the 41-250.

In the 41-280, the wire was quite a bit shorter and just hanging into space, and I thought the other routing was neater. I no longer have that wire to measure the length. Is there a procedure to trim and route it so that it works properly?

By the way, I have two 46-350 portables, and each one has a short length of wire sticking up from the volume control and not connected to anything on one end. Is that the same thing?

Thanks.

- Ron Ramirez - 06-05-2007

Hi John

In essence, a "gimmick" is a very small capacitance not in the usual capacitor package, but instead, a couple insulated wires twisted together or, in this case, a wire twisted around - but not making electrical contact with - a metal terminal.

In the case of the 41-250, 41-255, 41-280, et al., the wire should run through the terminal of the variable capacitor and then folded back. If it is not routed in this fashion, the radio will not work properly. In your 41-280 that has the wire just hanging in space, that radio will not work right until you run the wire through the terminal and fold it back (if you have not done that already).

The 46-350 wires you describe is something entirely different. I do not have the service info for the 46-350 handy, but it seems to me that was done as a test point?