SB-300 LMO warble

[Stu Lyon]

Hi Bill,

First off, the LMO is capacitive tuned -- not inductive. Your thinking of
Collins or Drake.

The problem is the wiper on the capacitor rotor. If needs cleaning which is
an easy job once you get the LMO out of the receiver. To remove the LMO, the
front panel should be removed although some have said this wasn't necessary.

With the LMO out, remove right, top, and front/bottom panels. Do Not remove
the left panel. What you now see is a worm-gear-driven capacitor. The job
now is to clean the hardened grease around the worm gear and the gounding
wiper on the capacitor. I use both WD-40 and DeOxid (sp?). Be careful not to
bend or any way disturb the wiper. One problem with doing this is that
there's no way of knowing if your doing any good until the LMO is back in
place so don't stint on the spraying and rotating the cap end to end. I have
also loosened the preload on the worm to make the turning a little easier
but I'm not necessarily recommending this.

When you put the LMO back in make sure the shaft is perpendicular to the
front panel as described in the manual and install the panel with its bottom
edge about 1/16" below the chassis bottom edge and the two edges parallel.


73, Stu W6CUX
Winnetka, CA
slyon at pacificnet.net

----- Original Message -----
From: "Bill Evans" <wb4css at MAC.COM>
To: <HEATH at LISTSERV.TEMPE.GOV>
Sent: Tuesday, May 06, 2003 10:47 AM
Subject: SB-300 LMO warble


> I am rebuilding a SB-300 and the LMO is erratic when tuning.  It is
> stable when I am not tuning,  With my frequency counter on the output,
> I watch it jump around plus and minus 20-50 Hz as I tune.  Since it is
> a slug-tuned coil, what can I do to make it smooth again?
> Thanks for the help.
>
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