[Heathkit] HW-101 questions.

Edward B Richards zuu6k at juno.com
Tue Apr 26 15:49:57 EDT 2005


Hi Ken;

That is not an unusual mod. I have done it to various receivers. The idea
is to supply the VFO with constant filament voltage, even when the radio
is turned OFF. This keeps the oscillator tube and compartment warmed up
to reduce frequency drift when first turned ON. Maybe he had it in an
unheated garage or something. He probably used an unused pin in the plug
along with one of the two that go to the switch, to supply 120 VAC from
the power supply. Some manufacturers, Hammarlund for one, have done this
too.


73, Ed Richards K6UUZ
AMI member #1534
 

On Tue, 26 Apr 2005 12:11:34 -0700 "Kenneth G. Gordon"
<kgordon at moscow.com> writes:
> I am working on an HW-101 that I bought recently for a very 
> reasonable sum. 
> 
> It appears all OK cosmetically, and the electronics seem all 
> right...except for one thing: the filaments of the 6AU6 that is 
> mounted on the top of the VFO box won't light.
> 
> Upon closer examination, I find that the previous owner has 
> added a separate 110VAC to 6.3 VAC filament transformer 
> under the deck near the power connector, and has, apparently, 
> rewired the power connector so that there is 110VAC available 
> between the normally unused connection and GROUND (!). He 
> then wired the output of this transformer directly to the VFO 
> buffer amp 6AU6 V-20.
> 
> Has anyone here ever heard of such a mod, and if so, why was 
> it done?
> 
> Ken Gordon W7EKB
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