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

[Peter Bertini]

Hi Al

I'm still well into the idea stage on this rig! Hi. I'd still like
to drop the AC line voltage a bit, maybe I'll see if there's
room to add a filament transformer for line bucking duty
under the chassis.

If you happen to know or remember, I could use a hint as
to what stage is controlled by the RF drive pot.  I'm going
in circles following the maze in the switches.

Pete

On Sun, Jul 18, 2010 at 1:48 PM, Al Parker <anchor at ec.rr.com> wrote:

> 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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