[Hallicrafters] HT-37 Questions

[Al Parker]

Hi Kevin,
    It sounds like you've got a nice project, I hope you do get it squared
away for F.D., and for further use after.  Yes, the power xfmr is a common
faliure item in the HT-32/37's.    My HT-37 did fine for a week or so, then
the xfmr went out, 5v winding to HV & some to gnd.  My HT-32 has a Peter
Dahl xfmr in it 'cuz it did it yrs ago.
    I'd suggest putting heat under it for a day or 3 to make as sure as
possible that it's not got any moisture.  Use a 60 watt light bulb, or one
of those small cube spaceheaters that's abt a 10" cube.  Try to get it up to
almost too hot to touch (that's abt 135-140F), and soak it there a day or
so.  Do use a variac after that, as you planned.
    And replace the rectifiers with SS to reduce load & heat in the xfmr.
I suppose it might help to use the now unused 5v winding as a buck winding
in series with the primary to reduce voltage, but that will put some slight
heat load back in there -- or just leave the variac set at 90-95%  ;-)  The
best bucking arrgt is to use a separate 6v xfmr.  I think someone's put that
ckt on BAMA somewhere.
    You might want to replace the selenium rectifier in the bias supply with
a SS diode, too.  It has high votage drop to begin with, but gets much worse
with age.  There's little voltage drop across the new diode, might need a
series resistor to drop it into the range of the pot,
    Take a look at my website for some ramblings I made on the HT-37.  Maybe
something there will help you out - I do incl. a section on going SS in the
rectifiers, an easy job, and very worthwhile.
    Keep us posted on your progress & success.
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info

----- Original Message -----
From: "Kevin Berlen" <kberlen at ticz.com>
To: <hallicrafters at mailman.qth.net>
Sent: Sunday, June 01, 2003 10:58 PM
Subject: [Hallicrafters] HT-37 Questions


> I am getting ready to fire up a HT-37 that has been dormant for
> many years. I don't know much about this rig, but it looks good
> and seems to be complete. I remember reading on this list that
> the power xfomers are a problem spot. I plan to bring it up slowly
> on a variac to hopefully reform the electrolytics, but is there anything
> else that I should or should not do? My QCWA chapter is hoping to
> have a boatanchor op position at a local club Field Day location
> using this rig for the TX portion and a R-388 on RX. TIA for any words
> of advice. 73,
>
> Kevin, K9HX
>
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