SB102 LMO & shaft coupler fixed!

[Wally Erikson]

Hi all;
     Wow, this list really works.  THANKS to all who responded to my calls
for help.  A through cleaning of the LMO got it back in service.  A trip to
the hardware store solved my shaft coupler problem.  Sorry for the late
reply but any spare time lately has been taken up working DX on 10 M with
my SB-102!
     Many of you asked about the LMO cleaning instructions so here is the
correspondence between Bob Norgard and myself...


Wally,

I have repaired two LMO's successfully that had very bad stability
problems.  They were terrible, and one of them failed to oscillate on
the upper half of the dial.  I first removed the bottom, and then the
foil tape from the top.  I used a non-lubricating no-residue contact
cleaner to clean the tuning capacitor contact points.  This was done,
followed by about 100 cycles end to end, then more cleaning.  When
this was complete, I took a hair dryer to dry up the condensation.
Finally, I used a 4" piece of wire with a dab of lubriplate (white
grease), and put the smallest amount on the wiping points, and cycled
it a few more times.  I also re-applied a little to the internal
gears.  On the electrical side, I replaced all of the capacitors on
the top of the VFO, which are part of it's regulator.  ( a good
replacement would also be a modern 3-terminal voltage regulator, but
the old zener workes fine. )

You may have already done this, but I didn't think it would hurt to
let you know what I tried.

Good luck!

73,
Bob Norgard - KL7FM

PS: For me, the HARDEST part was getting the xxx thing out of there
and back in without destroying something.

Thanks for your informative comments Bob,
     I'm trying to see these contact points you speak of.  From the bottom,
I can see that all the fins of the fixed side of the main air variable
tuning cap are soldered together and connect to the smaller air variable
tuning cap.  Their's a copper strip that rubs on both sides of the main
tuning shaft, is that it?  I don't see any other wiping points.  I have the
numbers TRW800668 110-48 stamped in the top of my LMO, do you?  Can you get
to chat at www.yahoo.com? Can I call you an evening this week?

Thanks

Wally


Wally,

I believe that I only removed the bottom so that the cleaner would run
out.  That, and possibly to apply some grease to the gear.  Remember,
I did this a year ago.  Looking in the top hole, I remember that the
capacitor shaft, at least on one end, had a groove cut in it, and a
bifurcated spring/contact was in it.  Like a fork with only two
prongs, even slightly bent like a fork, and this was saddled in the
groove on the shaft.  I don't remember if it was copped colored, or
stainless.  I do know that it had dried grease on it, probably keeping
the shaft from grounding properly.  You have to try to spray this
directly.  Use a flashlight to see it better.

Now, I believe that I used "Blue Shower" cleaner.  Got it from one of
the local electronic parts stores in Anchorage.  Radio Shack may have
something similar.  Even a Napa auto-parts store would have something
that may work.  I think any "contact" cleaner would be fine, but watch
out for anything that may harm plastic.  I knew a guy that used
"Flux-Off" on the wrong thing and dissolved the front right off of a
transistor radio case.  Some "tuner" lubes leave a heavy blue grease
behind.  This is OK to lube with afterwards, but I never spray it in
the VFO.  I always spray that stuff on a sheet of paper or foil, then
use a toothpick to apply it.  Ever try to "spray" a drop of grease?

I never adjusted anything on the VFO, except for the external
adjustment to get upper and lower sideband to track.  And I never had
that 21kHz offset you mentioned, but then haven't worked on that many.

I left my VFO regulator the same, no mods, just replaced all of the
electrolytics.

When I finished, the old foil was flattened and re-applied with
contact cement.  If that was ruined, anything, even regular foil glued
on would work.  Probably there to keep the dust/bugs etc out.

Can't remember the number, but there was a service note out from Heath
that says that if you remove the VFO, not to use the lockwashers to
put it back on.

Use flat washers and self-locking (nylock) nuts.  This is so that the
VFO will creep along the chassis with temperature changes, and not
flex the sides of the VFO,  (or so I'm led to believe).  It is
supposed to increase VFO stability.  There is a site somewhere that
has all of those old Heath SB's, listed by model number.

Good luck, Wally.

73,
Bob

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