[Hallicrafters] Some HT-37 questions

[David C. Hallam]

I've been thinking that it might not be too hard to rewind a transformer and
certainly cheaper than paying to have it done.  I think all that you would
be need would be a fixture to hold the core mounted on a shaft in a bearing.
The shaft could be turned by hand or through a reducer by a very small
electric motor.  Also, you would need a counter attached to the shaft to
keep track of the number of turns, a digital camera to take pictures as you
go along, and pencil and paper to keep lots of notes.  A simple payoff for
the spool of wire with a drag brake to keep the spool from running ahead of
the winding would be desirable.  I think all of this could be fabricated
from metal stock and other parts available at the hardware store with
nothing more than a hacksaw, a drill, and a tap and die set.

The quality of magnet wire available today is much better than what was
available when the transformer was manufactured.  Then too you could adjust
the turns ratio to account for the higher line voltage we have today.

David C. Hallam
KC2JD

-----Original Message-----
From: hallicrafters-bounces at mailman.qth.net
[mailto:hallicrafters-bounces at mailman.qth.net]On Behalf Of Philip Atchley
Sent: Saturday, November 13, 2004 5:03 PM
To: hallicrafters at mailman.qth.net
Subject: [Hallicrafters] Some HT-37 questions

Hi Y'all,

I have acquired a Hallicrafters HT-37 HF transmitter that is very nice
physically, electrical status unknown.  This will probably be a "overhaul
project" later this winter (when I finish the SX-101A and the BC-1004
presently on the bench, they both belong to friends). But I've received some
Emails about the HT-37 that have me a little concerned.

Apparently they are known for power transformer failures.  Quote, "It's not
a matter of IF they'll fail, just when they'll fail".

Taking this into consideration, I have some questions as I deliberate the
upcoming task of overhaul (I'd hate to put a lot of work into it and find
the transformer is already shot).

1.  How can I determine if it's already failed?  Does it smell "smoked" or
show other indications (I know some failures can be invisible).

2.  Would it be safe to pull both rectifier tubes out and test it that way
for failure, checking for tube filaments, Voltage on the plate connections
of the rectifiers etc?

3.  Assuming the transformer is good, are there any things that I can do to
reduce/eliminate the chances of transformer failure.  Things like putting a
lamp in the case for a week or two to "cook it", solid state rectifiers,
fans, separate filament transformer to reduce load on the main transformer
etc?

4.  Are there any other "issues" with this rig?

5.  FINALLY, if the transformer IS already bad, and having a slim wallet,
would it be realistic to pursue fixing the transmitter up, or would I be
much better off "parting it out (It's really quite nice overall)?

73 de Phil,  KO6BB
http://users.mercednet.com/beaconeer/
Merced, Central California, 37.3N  120.48W  CM97sh

***************************************************
* RECEIVERS:                                      *
*  #1. Homebrewed "Mitch Lee" Design              *
*  #2. Hallicrafters SX-71 (1955)& VLF Converter  *
* ANTENNAS:                                       *
*  #1. 20 Meter long "loaded" Sloper oriented E/W *
*  #2. Half Sized G5RV Inverted Vee oriented N/S  *
*  #3. Roof mounted Hustler 6BTV 6 band Vertical  *
*  #4. 15 Meter-band Inverted Vee oriented NE/SW  *
*                                                 *
* Number of different NDB's heard: 974            *
***************************************************

______________________________________________________________
Hallicrafters mailing list
Home: http://mailman.qth.net/mailman/listinfo/hallicrafters
Help: http://mailman.qth.net/mmfaq.html
Post: mailto:Hallicrafters at mailman.qth.net
----
List Administrator: Duane Fischer, W8DBF **for assistance**
dfischer at usol.com
----
Hallicrafters Collectors International: http://www.w9wze.org