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Hello. Brand new to the forum and hope that some of you folks can help me out.
First off i have no experience in testing coils, and i know i have alot to learn yet. But looking over the chassis of the 71h i see that the single wire that runs up from the inner RF coil length and attaches to a lug is severed. I have decent soldering skills therefore i'm wondering if i could just solder a piece of 32 gauge wire to repair it? Or would this throw the coil out of wack? If this isnt possible where could one find a replacement coil? Part # is 04339. thanks in advance.!
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Are you talking about the gimmick cap wire? This is a wire which connects to the primary winding terminal and wraps around the secondary winding with no actual connection at the opposite end. It serves a a very small coupling cap which increases sensitivity at the high end of the band.
If the actual primary or secondary winding wire is severed where it connects to its terminal, then you can try splicing it with a small piece of similar wire. This should not be a problem as long as you make a reliable solder connection and keep the wire length short.
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Welcome to the forum, Dirk.
It's good to have you !
Kenneth
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Thanks for the reply Mondial, sorry for not replying sooner as i was on vacation and did not have Internet access.
I do not see a gimmick wire....and cannot find info regarding the wiring to this RF transformer, anyway here is a pic which clearly shows the inner winding wire which i think would connect to the left lug as it seems to be the correct length if i put them together, perhaps this is the oscillator part of the rf transformer? how would i test to make sure these 2 wires indeed connect to each other? thanks in advance for anyones help.
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It appears that the broken coil wire does connect to the left lug. Does the left lug black wire connect to the antenna terminal of the radio? It seems that the broken wire connects to the primary of the coil which should be the antenna input.
Although Philco seems to call it the RF coil, it is more usually called the antenna coil. It is not involved with the oscillator as it couples the antenna signal into the grid of the RF amp tube.
I would try splicing the broken wire and see if you then have continuity from the left terminal to the lower right terminal, which should be the connections to the primary winding.
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Thanks once again mondial! If you look at the pic close you can see a thin wire just above the bottom red wire...this runs up the tube from the other side of that inner coil and attaches to the lug on bottom right corner...this lug then attaches to the antenna.
ill try connecting the severed wires off the one side of the primary [/align]within the tube which wont be an easy task! As this wire seens to be sheilded with silk, is there such thing as a conductive adhesive? This would make the task a little easier.
Posts: 39
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City: Medicine Hat, Alberta canada
Thanks once again mondial! If you look at the pic close you can see a thin wire just above the bottom red wire...this runs up the tube from the other side of that inner coil and attaches to the lug on bottom right corner...this lug then attaches to the antenna.
ill try connecting the severed wires off the one side of the primary [/align]within the tube which wont be an easy task! As this wire seens to be sheilded with silk, is there such thing as a conductive adhesive? This would make the task a little easier.
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No there is no such thing as adhesive for gluing wires. Magnet wires are cleaned and soldered.
You can use fine grit sand paper or an Exacto. Be careful not to cut it off, just scrape.
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Ok thanks morzh....ill give it a try.
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On old wire a lot of the time the soldering iron will burn off the enamel coating. The new stuff has a real tough coating that requires scraping. (carefully)
Terry
Ps Welcome to the Phorum!!! Enjoy
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For a wire of a reasonably visible gauge one of the way used to be quickly move it through a lit match fire and dip in alcohol. The burned enamel would readily come off.
However a very thin wire, or a thicker wire if you hold in in the flame longer then needed would melt. So you gotta be careful.
Well, anything done to a very thin wire has to be done very carefully.
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As Terry mentioned, heating the end of the wire with a fine tip soldering iron and coating with solder should remove the insulating enamel. It will be very difficult to scrape it since the coil appears to be wound with Litz wire. Litz is composed of multiple strands of very fine enameled wire with an overwrap of silk or cotton. Try heating the ends until solder sticks to them and then join together. If you get continuity through the coil then all should be well.
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Yeah litz is a pain in the hiny to clean. BTW that mentioned flame/alcohol thing worked well with litz.
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If turns out that you are unable to make the connection to the coil, it's not too hard to wind a new one. Get one of those clear plastic sewing machine bobbins and wind it full of wire that is about the same gauge as the original wire, the exact number of turns isn't too critical. If you have a sewing machine, you could probably use it to wind the bobbin. If not, put a bolt through the bobbin and chuck it in a drill. Mount the bobbin inside the outer coil form and you are all set.
Steve
M R Radios C M Tubes
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there is not so many turns to warrant all this headache. I would just wind manually.
