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Old June 3rd 08, 01:17 AM posted to rec.radio.amateur.boatanchors,rec.antiques.radio+phono
Chuck Harris Chuck Harris is offline
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First recorded activity by RadioBanter: Jun 2006
Posts: 270
Default How linear are Heathkit SB series LMOs?

Kim Herron wrote:
Hi Chuck!!
I've fixed several of these over the years, and what I've found
is that the ground wiper on the capacitor gets dirty (see Bill Turners
response). I'll expand on what Bill said. These things tend to lose
their ground and if it's real bad, you'll get a "warble" when you tune
the radio across the band. If you partially disassemble the LMO, you
can get to the cap and clean and regrease it, and then you can get to
the adjustments inside to be able to re-linearize the thing. I've
gotten many of them to track almost as close as a Collins PTO, easily
less than 1/2 kHz off per 100 kHz. You'll find that TRW used low value
caps to pad the things and usually very little actual repair of them is
needed. FYI, you WON'T find any good info on the thing because Heath
didn't want you inside of it in the first place. Draw a schematic so
you have something to work from.


Hi Kim,

The schematic for the solid state LMO is on bama in the Heath section.

Heath may have not wanted people inside of the LMO, but in the later years,
many an adventurous soul went in anyway.

-Chuck