[Hallicrafters] HT-32 PTT and CW break-in mods?

[Al Parker]

Hi agn,
	My article does include small value series resistors with the diodes to 
limit initial current.
	I would not use the 5v windings in bucking service to reduce the AC 
input voltage for the same reason that they should be removed from the 
circuit -- to eliminate a common failure mode.  I have had 2 of these 
transmitters that have failed in that mode so it's not just theory.
	Note that this is a SSB/CW transmitter, and the load on the xfmr varies 
as you put out a signal, it is not essentially constant as it is in a 
receiver.  Additional heat load due to any increase in voltage has 
plenty of time during receive or key up to be dissipated.  The low 
voltage isn't increased a lot, and the increse in high B+ is only 
applied to the final tubes, which can stand even more.
	Your mileage may vary, as may the opinions of others.
73,
Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 7/18/2010 1:30 PM, Peter Bertini wrote:
> Hello  Yes, I did find  that webpage in my searches.  My
> only caveat would be the concerns raised by W8JI
> http://www.w8ji.com/power_transformer_stress.htm
> I would further suggest adding a few power resistors
> in series with the diode cathodes to reduce the peak
> surge charging current. One other possibility would
> be to wire the now vacated 5-volt filament windings
> in series with the primary winding to reduce the turns
> ratio and further reduce transformer stress.
> pete k1zjh
>
> On Sun, Jul 18, 2010 at 1:22 PM, Al Parker <anchor at ec.rr.com
> <mailto:anchor at ec.rr.com>> wrote:
>
>     hI agn Peter et al,
>             I forgot (common thing nowadays), that article from a May 64
>     issue of 73 mag is on my website, take a look at
>     <http://www.boatanchors.org/HT37.htm> down at the bottom of the page.
>             You also should be interested in the section on "solid
>     stating the HT-37" (the HT-32 & -37 are essentially the same xmtr
>     except for the method of sideband generation).  It is advisable to
>     remove the 5v filament windings of the power transformer from the
>     circuit by going solid state at the rectifiers.  A common failure
>     mode of the HT-32/-37 is for the HV winding of the xfmr to short to
>     the 5v filament winding, or/and to ground, thus trashing the xfmr
>       It's a simple change which can save you future anguish.
>
>     73,
>
>     Al, W8UT
>     www.boatanchors.org <http://www.boatanchors.org/>
>     www.hammarlund.info <http://www.hammarlund.info/>
>
>     "There is nothing -- absolutely nothing -- half so much
>     worth doing as simply messing about in boats"
>     Ratty, to Mole
>
>     On 7/18/2010 12:51 PM, Peter Bertini wrote:
>
>         Hello to the group
>
>         I just traded for an early SX-32 transmitter, and I'm going
>         cross-eyed trying to following the relay keying circuit through
>         the maze of operating and function switch contacts.
>
>         So, to make my life easier--is there a good source for
>         modifications to allow for VOX operated CW keying and
>         changeover,  as well as a means to add manual PTT
>         that also disables the VOX feature?
>
>         Pete
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