[Hallicrafters] Off-net correspondence placed on-net.

[Al Parker]

Hi John, Skip, et al,
    I'll expand a bit on "SS diodes"  it's just replacing the tube type
rectifiers (both of them in this instance) with solid state diodes.  This
reduces the heat loading on the pwr xfmr, and by also removing the
filament leads you remove the HV on them inside the xfmr.  Hallicrafters
power transformers haven't stood up well with their advancing age, they
often develop HV to filament winding shorts, and sometimes also to ground.
These failures can be attributed to deterioration of the insulation by
heat and or moisture.  I've had it happen to me in an HT-37, an SX-101,
and an SX-42.  Also I have bought both an HT-32 (which is used regularly)
and an SX-62, which had already lost their pwr xfmr.  That's why we so
often hear the caution to warm up a new acquisition with unknown history,
or any one that's been stored a long time, by putting heat under it with a
light bulb, etc, for a day or 2.  Then slowly increase AC line voltage
just to be sure, and to allow filter caps to reform if they have't been
replaced.
    To see some details on the SS'ing of an HT-37/32, take a look at one
of my webpages:
<http://www.thecompendium.net/radio/HT37.htm>
    The SS stuff is down toward the bottom.  I've got some pix, a sketch,
and some notes/comments there and I hope it'll be of help.
    Skip, you might want to take a look at:
http://www.thecompendium.net/radio/filtercap.htm
to see what you can do if you're running out of room to fit discrete
electrolytics under the chassis to replace the cans.  It sounds like
you've done a thorough  job in there.  Was the rig operating before you
started, or have you just received it "as-is"?  (as-was?)
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info

----- Original Message ----- 
From: "John Cusick" <john at cusick.ws>
To: <hallicrafters at mailman.qth.net>
Sent: Wednesday, October 08, 2003 9:20 PM
Subject: Re: [Hallicrafters] Off-net correspondence placed on-net.
>
> I came upon an HT-37 a few years ago that looks like its complete and in
> good shape other than the previous owner must have died of cancer from
> smoking like a fiend based on the very "sticky" condition of the HT-37.
> I put it in a closet and have yet to even plug it in. Anyway, I've been
> following the HT-37 threads closely since it may be time to start
> tinkering. They have been extremely helpful.
>
> I have some old electronics and radio experience, now dulled from lack
> of practice, and one of the things that always confuses me is when
> someone offers advice like "just put the SS diodes...".
>
> What are "SS" diodes?
>
> Regards,
>
> John C.
>
>
>
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