Philco 37-660 Replacement IF Transformer Proposal - Printable Version

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Philco 37-660 Replacement IF Transformer Proposal - davemc - 10-23-2017

The second IF transformer on my Philco 37-660 has an open primary winding. I did some exploratory surgery but the winding appears to have a break somewhere in the inside of the winding. No breaks at the terminals, or anything else obvious (other than some "green" areas). I unwound turns from both ends as far as I could go. The original is for 470kHz. Primary is 12 ohms, and the secondary is 8 ohms and appears to be tapped. I have plenty of 456kHz donors, but only one 470kHz. 

I am wondering if I can get away with using an IF transformer from a Philco 37-34, which is a 6-volt DC set using 2-volt battery tubes. The winding resistances of the 37-34 transformer are virtually the same as my original: primary 11 ohms, secondary 7.5 ohms. The coil and trimmer assembly even fits the original shield EXACTLY and the alignment holes line up. My main worry is that the original secondary (marked 8 ohms) appears to be center tapped. But when I measure the winding resistance at the leads it measures 8 ohms not 4 ohms. And surgery does not indicate a tapped winding.

Just curious if I can get away with this, or if there is some fundamental reason why a battery radio transformer would not work in an AC set.

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RE: Philco 37-660 Replacement IF Transformer Proposal - vinzer - 10-23-2017

It should I just concerted a battery set to ac it worked ok.

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RE: Philco 37-660 Replacement IF Transformer Proposal - Radioroslyn - 10-23-2017

My best guess is that on the '660 the If transformer tap is to provide a lower impedance source for the detector. I would use it (one from the '34) with the wire connected to the tap moved over the top of the winding. Don't think there is an issue.

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