[Boatanchors] FW: Replacing the 6AU6 with a 6AH6 in the Heath VF-1 VFO

Thu Dec 13 11:40:10 EST 2012

I had the same frequency-jumping problem.

In my VF-1 as a teen-ager (I'm now 70) I fixed it by hauling out my
grandfather's American Beauty monster soldering iron and re-heating the
trimmer tabs the were soldered to the vfo chassis.

Apparently my then Weller 100 watt or so soldering iron couldn't keep up
with the heat sinking ability of the chassis.

After flowing solder well with the "tinner's iron" which as I recall is what
the American Beauty was called -- it was used for soldering sheet metal
seams -- the vfo never jumped frequency again!

The American Beauty, which now resides in my garage workshop, is almost as
big as a rolling pin -- and takes lots of lots of time to heat up and cool
down.  Sometimes nothing beats the heat storing ability of a really big
copper tip!

Mike/
K5MGR
__________________________________________

Mike Langner
929 Alameda Road NW
Albuquerque, NM 87114-1901

(505) 898-3212 home/home office
(505) 238-8810 cell
mlangner at swcp.com

-----Original Message-----
From: boatanchors-bounces at puck.nether.net
[mailto:boatanchors-bounces at puck.nether.net] On Behalf Of gary skillicorn
Sent: Thursday, December 13, 2012 9:34 AM
To: gzook at yahoo.com; boatanchors at puck.nether.net
Subject: Re: [Boatanchors] Replacing the 6AU6 with a 6AH6 in the Heath VF-1
VFO

I had a VF-1 problem I never did solve in my long gone novice days.
Operating with a DX-60 the frequency would jump randomly several hundred
hertz. It didn't seem to be heat nor mechanically induced. It still bugs me
many years later. Wondering if others had this problem and if ever solved
it.  Interesting story about Heath. Thanks. A great outfit. They gave an
affordable start for a lot of young fledgling hams.  Wonder how much lead
from solder fumes we sucked up?  Gary  K3GS  > Date: Thu, 13 Dec 2012
08:18:15 -0800
> From: gzook at yahoo.com
> To: boatanchors at puck.nether.net
> Subject: [Boatanchors] Replacing the 6AU6 with a 6AH6 in the Heath 
> VF-1 VFO
> 
> Recently, I have been asked as to how I came up with the idea to replace
the 6AU6 in the Heath VF-1 VFO with a 6AH6 and for the other changes I
recommend which are to replace the 0A2 screen voltage regulator with an 0B2
and run the VFO from a regulated 150 VDC source.  As such, I thought that
others might be interested in this.  The following is the answer that I
gave:
> 
> The idea for replacing the 6AU6 in the Heath VF-1 actually came from the
Heath Company.  The very first TX-1 Apache transmitters used the 6AU6 in the
VFO.  However, the stability was just not satisfactory for use with the
SB-10 SSB adapter.  After some experimentation, it was found that when the
6AH6 was used in the VFO without any changes to the circuitry, the stability
improved immensely and the only difference was that the trimmer capacitors
for calibration on each band had to be adjusted slightly to compensate for
the difference in inter-electrode capacitance.
> 
> Since the tube is not operated anywhere near its limits, the fact that the
maximum plate dissipation is slightly different does not enter into the
equation.
> 
> I grew up 35 miles from the Heath plant (LaPorte, Indiana) in St. Joseph,
Michigan.  The mailing address was Benton Harbor but the actual location of
the plant was on Hilltop Road in St. Joseph.  After getting my driver's
license, I would occasionally drive up to the Heath plant just to "drool"
over the latest equipment.  Heath had a display room, where one could
actually purchase and take home equipment, that was located to the left as
one entered the main entrance to the plant.  If you had any questions about
any equipment, the person at the order desk would call back into the plant
and someone, often the lead engineer on the kit design, would come out and
answer your questions.
> 
> The engineer would often suggest changes to the equipment to improve the
operation and, usually, hand you a paper bag with some parts and a
schematic, sometimes "hand drawn".  There was never a charge for this.  One
time, I had a question about frequency stability on my DX-100 transmitter
and the engineer suggested replacing the 6AU6 with a 6AH6 and changing the
screen regulator to an 0B2 instead of the 0A2.  He also commented that this
worked great on the VF-1.  Although he didn't comment on using regulated 150
volts for a separate power supply for the VF-1, I tried that, using the 0A2
removed from the screen of the tube to regulate the external power supply.
That improved the stability even more.
> 
> Ever since then, I have recommended changing the VF-1 tubes to a 6AH6 and
OB2.
> 
> I never knew the name of the particular engineer who suggested the
changes.  However, if I remember correctly, he had been involved with the
design of the TX-1 Apache as well as the DX-100 and VF-1.
> 
> There were a number of Heath employees that were amateur radio operators
who were very active.  I used to work them on 6-meter and 2-meter AM.
> 
>  
> Glen, K9STH
> 
> 
> Website: http://k9sth.com
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