HW-101 VFO problem

[Stewart Lyon]

Hi Paul,
Stu again at my "home QTH email"
I looked up the alignment procedure as described in "The Heathkit
Technical Journal"  11/97. They were talking about a DX100 but I've used
this approach on other Heathkit VFO's.

The article is too long to quote but it essentally said to use the
trimmer to align at the low frequency end and adjust the coil at the high
end. If the spead is too narrow (as in your case), reduce the coil
inductance by turning the slug out -- if too wide, increase the
inductance by turning the slug into the coil.  The coil adjustment is
only rough and you will want to overshoot. The fine adjustments are made
by the trimmer.

As you have noted, since the VFO tunes backward, the low frequency end is
the high dial reading.

BTW, I just re-read the HX1681VFO procedure and they have you doing just
the opposite of the above (coil at the low freq, trimmer at the high). As
I recall, I never could get the VFO right until I did it the other way
around.

This should work !!

73, Stu - W6CUX
Winnetka, CA
ARRL Life Member

On Mon, 9 Nov 1998 09:26:39 -0700 "Paul K. Dean"
<wb9hgz at CHARLOTTESVILLE.NET> writes:
>Hi, everyone -
>
>I am bringing a "basket case" HW-101 back to life.  After many, many
>hours
>of work, I have it pretty close to going.  Wow, what a job it has
>been.  At
>any rate, I have an interesting problem with the VFO that I'd like to
>run
>by the group for comment.
>
>The problem is one of VFO tracking.  I can calibrate the "high end"
>using
>the coil slug as detailed in the manual.  The "low end" is about 120
>khz
>off, but can be brought in using the trimmer.  At that point, the
>"high
>end" is off.
>
>To make a long story short, going back and forth, I could get the unit
>to
>calibrate only within 80 khz.  (In other words, if the "high end" is
>set,
>the "low end" is off 80).  Took the vfo apart and tested all the
>capacitors.  All tested OK insofar as I could tell using my Heath
>"Magic
>eye" "condenser" checker.  Found several caps not positioned as per
>instructions, re-installed so everything was as per the photograph and
>diagrams. Calibration is better, but still, I run out of trimmer while
>the
>lower end is still 20 khz off.
>
>Put on a frequency counter...... at the point of running out of
>trimmer,
>the vfo reads 5.000 at the high end of the band and 5.480 (should be
>5.500)
>at the low end.  Can't bring it up any farther.  Trimmer screws are
>all the
>way out.
>
>Any ideas or thoughts would be appreciated!
>
>Thanks and 73,
>Paul, wb9hgz
>

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