[Hallicrafters] Re: HT-3X Bias Adjustments

[Mark Shaum]

----- Original Message -----
From: <wb8jkr at juno.com>
Subject Bias Adjustments


> exceeds the rating of the capacitors. I suggest
> that Hallicrafters designed the 6146's to draw a
> certain amount of minimum current to provide the
> required minimum current load for the choke input
> supply. Getting rid of this minimum current may cool
> off the tubes a bit, but may cause you a problem in the
> HV supply filter.
>
> Mark  WB8JKR
>

Exactly!  In their infinite wisdom Hallicrafters chose to allow the pair
of 6146's to act as B+ bleeder resistors.  With my line voltage here, my
stock HT-32B had over 900 volts on the plates of the tubes when in
standby mode.  I have a surplus solid state HV relay in mine which
places a 20ma load on the B+ when the rig is NOT in transmit by
switching a resistor in parallel with the existing B+ bleeder.  It is
switched out during transmit so as not to add 20ma more to the draw on
the B+ while transmitting.  Resting B+ at idle is now about 800 volts.

Pros are less B+ on the filter caps and tubes most of the time.  Both
may last longer.

Cons are two, a bit more heat is generated and you have to modify the
factory designed circuitry in  a classic rig.

Mark, K9TR