Truetone transformer interesting find.

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Truetone transformer interesting find.

Post by simplex1040 on Mon Jul 15, 2013 11:39 pm

I am working on  Truetone radio which I found had a short in the B+ Lit my 100 watt dim bulb up bright. So Since I had recapped said Truetone I went looking for the short in my work. Finding none I measured between CT and the HV secondaries One was 135 ohms the other 1 ohm. I had found my short. So I measured again to be sure. 135 ohms one side 0 on the other, now what was shorted was not open. The only thing I did was scoot the radio over, there had been no power applied between measurements.  So I opened up the transformer and here is what i found.



Red circle was one side of the center tap winding which was soldered to nothing, While green is one side of the HV secondary that was soldered to nothing but the CT wire had been touching it intermittently. (hence the short). I found the other wire (Yellow) that had never been soldered to green ( where it was supposed to be.

Factory defect is all I can imagine
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Re: Truetone transformer interesting find.

Post by simplex1040 on Mon Jul 15, 2013 11:40 pm

Ill show you my repair when I get it done
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Re: Truetone transformer interesting find.

Post by Resistance is Futile on Tue Jul 16, 2013 2:35 pm

I don't think it was defective wiring, but maybe corrosion at the connections that ate the metal away? Glad you found the problem. I'm sure if it were not wired then the radio wouldn't have played to start with and returned and sent back to the factory or sent to a repair shop. If it were maybe the had wrapped the wires around the terminals and either forgot to solder or used acid core solder and the acid destroyed the wire, or the wire got burned from a short elsewhere and just got put aside, because they couldn't troubleshoot the problem further, or it could have been a factory defect that was replaced and just not worked on because of repair costs.

Or the wires were worked on and the wires became too short. Who knows but fun to speculate though . confused
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Re: Truetone transformer interesting find.

Post by simplex1040 on Tue Jul 16, 2013 10:04 pm

Success on transformer surgery, I have B+ with no shorts

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here was my repair before I added insulation and dressed the leads better. It is now buttoned up and working.
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Re: Truetone transformer interesting find.

Post by Bill Cahill on Wed Jul 17, 2013 1:59 pm

Great job, Sim. Thanks.

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Re: Truetone transformer interesting find.

Post by simplex1040 on Thu Jul 18, 2013 10:11 am

After silver mica surgery Set is working. I have issue with no reception below 700 on the AM side. Either I have a short on the tuning gang on a bad osc tube.
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