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451Re: [VicRadioGroup] How to Fry your power transformer

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  • lbohn@shaw.ca
    Oct 2, 2012
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      I have tried to be vigilant about replacing the selenium bias rectifier with a silicon rectifier as well.  It probably isn’t a big concern with tube sets but I have a pinball machine that needs a “heads up”.  I’m sure the audio guys on the list have a lot more information about them than I have. 
       
      From: Lee
      Sent: Tuesday, October 02, 2012 11:27 AM
      Subject: [VicRadioGroup] How to Fry your power transformer
       
       

      I copied this from a posting on the hallicrafters mailing list that I recently joined, thanks to Lorne in Nanaimo. Thought this was quite interesting the the message calls a 5V4 a "death tube" anyone else heard or seen anthing along this topic line. Anyone know of other dangerous rectifiers prone to short out and ruin a radio transformer?

      From: "K4PRF, B. L. Pratt" <mailto:pratt%40knology.net>
      To: mailto:hallicrafters%40mailman.qth.net
      Sent: Monday, October 1, 2012 2:26 PM
      Subject: [Hallicrafters] HT-32 to HT-37

      Lesson learned the hard way. If you have one of these fine transmitters
      and if it is still using the 5V4 low voltage rectifier, your power
      transformer is in danger. If I remember correctly the problem is caused
      by a cathode to plate short in the 5V4 which opens the high voltage
      winding in the PT. These transformers are very hard to find and
      expensive if you can find one. I purchased a beautiful HT-32A several
      years back knowing that the PT was bad. I was able to order a
      replacement PT from the Peter Dahl Co. Expensive but a perfect
      replacement and runs very cool. I replaced that 5V4 with a 5R4 in this
      and my HT-37. I am told that those 5V4s have killed many a transformer
      and some call it a "death tube." You might while you are in there
      replace the selenium bias rectifier with a silicon rectifier. There
      have been many articles dealing with these modifications on the HT-32s
      and HT-37s.

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