HW-101 Warble Problem

[Kechkaylo, David]

Dear Jeffery Weiss:

Yeah, well it sounds like some instability to me, probably in the VFO
unit. Does it do this while you're tuning also? If the VFO had some
mechanical instabilities, once set, it may jump off frequency. This
could be due to some mechanical tension set up in the VFO. Or, it could
possibly be an electrical instability, too. I assume it does this on all
bands, and if so, then this rules out the HFOs.

I'd start by disassembling the VFO completely and check for improper or
cold soldering, loose or poor, but incomplete ground contacts, and
perhaps loose mechanical placement/assembly in there. Especially look at
the VFO tuning capacitor plates; both rotor and stator plates. Will
bumping the table on which the HW-101 sits make this problem appear,
too? Also look at the VFO capacitor gear and stops. Clean and tighten
the entire assembly, but most of all, check that VFO tuning cap and dial
drive mechanism. Try all this and see what happens. Also, make sure the
VFO coil slug isn't loose and "slopping" around.

Regards,

Dave K.

> ----------
> From:         Jeffrey Weiss[SMTP:weiss at tds.net]
> Sent:         Wednesday, November 11, 1998 3:02 PM
> To:   Kechkaylo, David; HEATH at LISTSERV.TEMPE.GOV
> Subject:      Re: HW-101 Warble Problem
>
> Hi, David,
>
> ** Reply to message from "Kechkaylo, David" <dkechkaylo at MDSROC.COM> on
> Tue, 10
> Nov 1998 17:37:24 -0500
>
>
> > Dear Jeffery Weiss:
> >
> > Many of the ball-bearing type of Jackson Drives used in several of
> the
> > Heathkit amateur products had this problem from time to time. There
> may
> > be spots on the dial as you're tuning around and you won't hear
> this;
> > other spots (depends on the point you are on the VFO cap rotation),
> and
> > you can't seem to tune the station in, it warbles so bad.....it is
> like
> > your "pie-eyed" or drunk.
>
> Can this problem exist when you're ON a station and don't touch the
> VFO knob?
> It warbles for me, then.
> CW signals , most noticeable, pop up and down slightly in frequency
> about a
> center frequency while I'm sitting back and just listening.
>
>
> If it really sounds like the same problem I will happily disassemble
> the darn
> thing as you suggest. Cheap fix!
>
> Thanks,
>
> Jeffrey N0IRR
>
> >
> > Anyway, the problem is almost always a mechanical one here.
> Sometimes it
> > helps if you disassemble the VFO unit entirely, meaning the
> mechanical
> > VFO tuning capacitor from the VFO unit where it is mounted, the dial
> > assembly, and the Jackson drive unit. Then carefully put it back
> > together, but try to do this without any mechanical stress.....just
> let
> > the parts fit back together like they're supposed to...like a glove
> with
> > no forcing, according to the manual. No need here to get involved
> with
> > the electrical assembly, just the mechanical VFO capacitor drive
> parts.
> >
> > Once assembled, tighten the front tuning knob set screws associated
> with
> > the Jackson drive after you've rotated the main tuning knob back and
> > forth a couple of times to make sure this drive and the VFO tuning
> > capacitor shaft are straight in line. Then tighten the set screws.
> This
> > makes sure, if the VFO cap is off center, you won't warp the Jackson
> > drive a bit as you go thru all the possible tuning rotation.
> Sometimes
> > it helps to squeeze the tabs tighter around the collar of the
> Jackson
> > drive, too, as this may make the tuning a bit stiffer to rotate, but
> may
> > reduce some of the "slop".
> >
> > On the other hand, in difficult cases, direct replacement of the
> Jackson
> > drive cures the problem altogether. I hope this helps. The SB-104
> uses
> > similar Jackson drives (actually two of them), and I absolutely HATE
> it
> > when the VFO warbles like that. The above explanation will sometimes
> > cure the problem on all Heath VFO units utilizing similar drive
> > mechanisms. If this solves your problem, then proceed to re-align
> the
> > VFO unit according to the manual. It won't be off by much, though.
> >
> > Regards,
> >
> > Dave Kechkaylo
> >
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