[Hallicrafters] Old Transformers

[Carl]

Interesting observation Todd but my experience is slightly different.

I dont remember a bad NC-173, 183 or HRO-50 transformer.
OTOH the NC-183D, NBS-1, HRO-50-1 and HRO-60 are notorious for it and with some its that .1uF paper cap from the B+ seondary to ground that takes them out. A 1000V or larger film cap is fine.

Any transformer can be taken out by bad caps and no circuit protection. However I believe Halli is unique with the saturation issue and it lasted into the SX-62A era from the late 30's.

For Collins all the 32V's had poor insulation quality in transformers and chokes, including audio.

My own near mint SX-15, 16, one of the 17's, 18, and one of the 28's were purchased with known bad iron, often the audio as well as always the power. Ive been lucky with the SX-42 and both 62A's as both are known troublemakers.

Ive managed over 2-3 years to obtain all good originals and then do a total electrical overhaul.

Everything now runs at 110-113VAC using bucking transformers, either full bench big ones or individuals.

Hallis are always fun!

Carl
KM1H



  ----- Original Message ----- 
  From: Todd, KA1KAQ 
  To: Carl 
  Cc: Larry Young ; hallicrafters at mailman.qth.net 
  Sent: Monday, June 18, 2012 1:54 PM
  Subject: Re: [Hallicrafters] Old Transformers



  On Mon, Jun 18, 2012 at 1:03 PM, Carl <km1h at jeremy.mv.com> wrote:

    Up to 100%. 


  If the unit hasn't been taken care of and older components haven't been replaced, it's indeed just a matter of time. Overall use matters, too. A set used now and then will probably last beyond us whereas one in daily or at least regular service is likely to give up the ghost sooner. That's where the component upgrades and reducing line voltage make a huge difference.
   
    Ive lost count to how many Hallis (and some other brands including Collins)
    Ive had in for service that had oddball replacement transformers or shorted
    ones and Id have to find a good original or have it rewound.


  National seems to be the worst for power transformers. Cannot recall how many HRO-50/60s, NC-173/183s and others I've come across with bad or replacement transformers. No doubt a combination of age, use, original materials, and overall maintenance. Elevated line voltage and old components being the highest long-term risks. 

  When it comes to audio output transformer failure, Halli leads the pack there. Fortunately they made enough models that shared the same parts that replacements are fairly easy to locate. Even if only to rewind.

  ~ Todd/KAQ


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