[Hallicrafters] HT-37 refurb/troubleshooting

[David C. Hallam]

I have owned several HT-32's over the years and every one has had the power
transformer rewound either when I owned it or before I bought it.  Also, I
have a HT-37 sitting near the bench that I will get to restoring some day.
Right now there is a Johnson Invader 2000, 2 - Invader 200's and a
Hallicrafters HA-6 6 meter transverter ahead of it.

There is no separate filament transformer in the HT-32/37.  If there were,
the problem probably wouldn't exist.  As Al says the primary failure mode is
a HV short to the 5R4 rectifier filament winding.  Replace the 5R4 with a SS
state rectifier and disconnect the 5 volt leads to its socket.  Don't worry
about the increase in voltage, the 6416's can handle it without any problem.

As far as the LV rectifier, 5V4, goes, that's optional.  They generally
don't cause any problem.  If you do decide to go SS with it too, you should
include a dropping resistor as the extra voltage there can be a problem.  I
use the Weber Copper Top 5V4 replacements in mine as they have all of that
built in in a nice package.  Some people get all hung up on the fact when
you SS the rectifiers, the plate voltage is applied before the heaters comes
up to full temp.  Maybe it is a problem and maybe it isn't.  Remember we are
dealing with miniature tubes here that heat up quickly and if you use
6146A's they are almost instant on anyway.  It's not like there are any
expensive transmitting tubes in there where warm up is a consideration.  I
have never had tube life issues with any of my HT-32's.

David
KC2JD/4

> -----Original Message-----
> From: hallicrafters-bounces at mailman.qth.net
> [mailto:hallicrafters-bounces at mailman.qth.net]On Behalf Of Al Parker
> Sent: Tuesday, January 30, 2007 3:17 PM
> To: W4AWM at aol.com; bluebirdtele at earthlink.net;
> hallicrafters at mailman.qth.net
> Cc: jdausilio at gmail.com
> Subject: Re: [Hallicrafters] HT-37 refurb/troubleshooting
>
>
> Hi folks,
>     I don't remember a separate fil. xfmr in there, so don't know where
> the primary leads for it might be, but do remove the filament leads from
> both pins of the rectifier socket(s) to totally remove HV from the fil.
> windings.  You can see some info/pix, etc. on one of my webpages:
> http://www.boatanchors.org/HT37.htm
>     Those HT-32 & HT-37 power transformers definitely do have a bad
> history of failure, usually the HV winding to 5v fil. winding, or one of
> them to ground.  I've had 2 with the problem
> 73,
> Al, W8UT
> New Bern, NC
> BoatAnchors appreciated here
> http://www.boatanchors.org
> http://www.hammarlund.info
>
> ----- Original Message -----
> From: <W4AWM at aol.com>
> To: <bluebirdtele at earthlink.net>
> Cc: <jdausilio at gmail.com>; <hallicrafters at mailman.qth.net>
> Sent: Tuesday, January 30, 2007 12:28 PM
> Subject: Re: [Hallicrafters] HT-37 refurb/troubleshooting
>
>
> > If you solid state the power supply, disconnect the filamant transformer
> > primary and secondary leads and isolate them since they are no longer
> needed.
> > Check to make sure that the HV is within specs since it will tend to be
> higher
> > with solid stare rectifiers installed.
> >
> > 73,  John,  W4AWM
> >
>
>
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