[Hallicrafters] HT-3x transformers

[Mark Shaum]

> I've always heard that HT-32 and HT-37s were prone to power
transformer failure,
> but I've been lucky.  Can anyone explain what the failure mode is,
and why these
> transmitters seem to fail more often than most?
>
> Is it a good idea to switch from 5R4/5U4 rectifier tubes to
solid-state rectifiers
> in order to reduce the overall current drawn from the transformer?
>

One item that Hallicrafters warns about has to do with the function
switch layout.  Many folks were known to flip to off accidentally when
using the function switch for T/R toggling.  With the usual
instinctive immediate flip back to on there is a chance of a pretty
good current surge depending on the phase of the AC.. that nice
"thwang" the tranny makes as it starts out at a peak of the AC wave.
Did that a couple times on the HT37 myself.

And about solid stating the HV, be careful.  My HT32B runs too high of
a voltage on the 6146 plates when in standby, over 850v even with the
5R4 in place..  I added a relay that actually switches in a bleeder
when not in transmit mode.  I'd leave the bleeder in all the time (it
does really improve regulation) but don't want to drag more watts out
of a tranny that gets warm anyhoo.

Mark K9TR

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Mark Shaum K9TR
email: k9tr at dtnspeed.net
http://www.mtco.com/~k9tr
Central Illinois Grid EN50hi  Zip 61721
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