[Hallicrafters] HT-37

[rdhalste]

> Hi Bob et al;
>
> Let me harp on my favorite subject....high line voltage. Today's official
> line voltage is 122 VAC. Consider that it was 110 to 117 VAC when these
> old guys were designed and built. I think that this is the reason so many
> power transformers get burned up. See BAMA home page, about 1/2 way down

I keep seeing this, but "in the old days" I lived at the head end of a log
distribution line.  My voltage was normally 125 back in the 60s and 70s and
I never lost a transformer. Lots of lightbulbs though.

My guess is that the cause is a combination of things..such as having set
around and soaked up moisture, leaky caps, resistors having changed to lower
values and even gassy tubes presenting higher loads that the equipment did
originally.

I may be wrong, but taken that the transformers that have set around for
years, and may have high leakage inside with possibly damaged insulation
from moisture. Then add the increased loads that are likely from the other
causes, and that I never had problems with 125 volts for years,  I'd place
my bets on this instead of high line voltages.

Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair? (S# CD-2)
www.rogerhalstead.com
> for a cheap and simple, but effective and efficient, way to reduce your
> line voltage to protect these jewels. You can build it yourself, buy a
> kit or get one built and tested. Sounds like this could be your problem
> Bob. Good luck.
>
> Ed Richards
>
> On Fri, 28 Feb 2003 01:17:03 -0500 "Robert Stachurski"
> <WB4RFF at worldnet.att.net> writes:
> > Many tnx for the welcome aboard.  tnx especially for those secondary
> > voltages on the pwr xfmr that really helps me out and those were the
> > same values I was getting voltmeter readings.   This old xmitter had
> > 40+ years of dirt, dust, crud and corrosion on it when I started and
> > most of it is now cleaned up.  The wiring under the chassis is
> > cotton covered and 99% of of the color coding has faded away but the
> > wire insulation itself seems to be intact.  When I lit of the
> > equipment there was not the heart-wrenching aroma of boiling tar or
> > whatever it was that was used in xfmrs so I came to a hasty
> > conclusion that the xmitter was repairable with some extra effort.
> > I did change out all of the electrolytic capacitors and resistors in
> > the bias supply but that bias was still reading a bit high and the
> > manual said that the bias voltage is VERY critical.  I did read the
> > specs for the 6146's in the RCA xmitting tube manual and all of the
> > voltages comming from the power supply are at a critical level.
> > When I replaced the resistors and electrolytics in the pwr supply I
> > used components that exceeded the specs in the parts list (wattage
> > and % tol. for the resistors ; voltage for the caps).  The
> > components that are made today are much smaller than those that were
> > made when this xmitter was first manufactured.
> > Ideally I would have liked to restore this HT-37 to museum grade but
> > a quick eyeball survey told me that this was an impossible task.
> > What I can do and have done is a lot of extensive repair and clean
> > up so that I will have a xmitter that works the way it is supposed
> > to.  There are many collectable items that gain in value because
> > they were used for their intended purpose; just ask any stamp or
> > firearms collecters.  I will let you know from time to time how the
> > work is progressing and in the meantime I will abide by a modified
> > version of the carpenters code  "check wiring twice and solder
> > once".
> > Are ther any ex-Navy ET's out there that might remember the ten
> > commandments of a tech?  It went something like this:
> >        Keep one hand in your pocket when working on high voltage
> > lest your shipmate finds you roasting on a piece of equipment
> >        and consoles your widow with copious amounts of wine and
> > beer!
> > Once again, many tnks for the welcome and info.
> >   73's Bob WB4RFF
> >
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