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I.F. Transformer rewind help. - Printable Version

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I.F. Transformer rewind help. - Greenhorn - 08-26-2016

Good Morning All,

The 38-93 that I am working on has a bad primary winding on the #2 I.F. Transformer (#32-2459).
My question(s) would be; is there a simple formula to calculate the length of wire required for re-winding ? According to the schematic there should be 17 Ohms across the primary. I have a spool of #38 wire.
I made a mess of the coil unwinding it, so I don’t know the original number of turns. Can length of wire alone be used to determine the finished coil without taking the number of turns into consideration?
Does the width/height of the finished coil matter as long as there is 17 Ohms of resistance?
Thanks in advance.

RE: I.F. Transformer rewind help. - KCMike - 08-26-2016

Hers a quick calculator. Might help if you know the approx. gauge of the old wire.
http://www.cirris.com/learning-center/calculators/133-wire-resistance-calculator-table

RE: I.F. Transformer rewind help. - Greenhorn - 08-26-2016

Thank You, this will be helpful. Maybe I can measure the length of the old wire then use the calculator to determine what gauge it actually is. Just guesstimating, I'd say it's at least 75'.

RE: I.F. Transformer rewind help. - GarySP - 08-26-2016

A little late now, but in the future run the point of a straightpin across the coil and count the number of "bumps" you encounter. This will tell you how many coils are in the winding. Then check the thickness of the wire with a micrometer to determine the gauge of enameled magnet wire you need for the re-winding. Take care, Gary

RE: I.F. Transformer rewind help. - Radioroslyn - 08-26-2016

(08-26-2016, 03:36 PM)GarySP Wrote:  A little late now, but in the future run the point of a straightpin across the coil and count the number of "bumps" you encounter.  This will tell you how many coils are in the winding.  Then check the thickness of the wire with a micrometer to determine the gauge of enameled magnet wire you need for the re-winding.  Take care, Gary

This method works well if the winding is just one layer. Typically the coils inside an IF transformer are multi layer and would be difficult to ascertain the number of turns. Good for rf and oscillator coils if there not too low in frequency.

RE: I.F. Transformer rewind help. - Radioroslyn - 08-26-2016

(08-26-2016, 12:53 PM)Greenhorn Wrote:  Thank You, this will be helpful. Maybe I can measure the length of the old wire then use the calculator to determine what gauge it actually is. Just guesstimating, I'd say it's at least 75'.

So I understand you like torture! Go here:  
http://www.oldradioparts.com/pg20.htm   and buy a 37-60 chassis or see if Gary will pull out the IF transformer and sell it separate. Looks like his got several chassis to choose from. It has the proper frequency transformer but may mount differently so mount it in your old can.

GL

RE: I.F. Transformer rewind help. - Greenhorn - 08-26-2016

Thanks guys. 

RE: I.F. Transformer rewind help. - GarySP - 08-27-2016

Thanks for the correction, Terry.  Probably should have mentioned would have to account for layers of windings as well.  Take care, Gary