[Hallicrafters] Old Transformers

[Gary]

   As I see it all the mentioned causes are valid but, I find that lack of 
iron to be a major factor and lets not forget, if the primary had more turns 
to reduce the volts per turn, this would keep the transformer from going 
into saturation. Less volts per turn (more copper) along with the extra iron 
is a major factor in figuring the cost. I just completed a rewind for a 
National HRO-50 power transformer. No load current at 120 volts was around 
50 mils. Volts per turn was .2620. I also rewound an HRO-60 and the no load 
current on the primary was 210 mils. The volts per turn was .5042. As you 
can see, the more the volts per turn, the more iron is needed.
My two cents.
Gary
----- Original Message ----- 
From: "Carl" <km1h at jeremy.mv.com>
To: "Todd, KA1KAQ" <ka1kaq at gmail.com>
Cc: <hallicrafters at mailman.qth.net>
Sent: Monday, June 18, 2012 2:23 PM
Subject: Re: [Hallicrafters] Old Transformers


> 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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