HW-101 dial drive slippage

[Ed Kotkiewicz]

rayfri wrote:

> would that be the same problem I'm having with my sb 100?  his symptoms
> sound almost identical to what i'm experiencing...
> Ray wa7itz
>

EK> Ray, the SB series uses an LMO (as opposed to a VFO) and a different (less
positive) method to couple the dial action over to the LMO.  Two conditions
happen with the SB gear.  First off the dial is regulated by a split washer
(beryllium) assy that has two washers that are flaired out on the ends and are
assembled, back to back, to form a pulley.  This pulley then engages the inner
ring of the actual dial.  If you take off a SB's tuning knob you will see a nut
holding the shaft assy.  If you loosen (not remove) this nut you can slide it
up or down, which engages the inner ring of the dial.  As you push (lightly)
downward, the dial ring is engaged by this back-to-back pulley and a friction
fit occurs.  Sadly, as time goes by, the these washers spread apart and the
friction fit becomes less reliable.  You can take the shaft nut off, lift the
shaft assy away from the dial and take it out through the back.  Now unscrew
the screw that is on the backside of the assy., carefully remove the washers.
You now want to re-flatten the surface to make the washers flat again.  Do this
very carefully.  Then re-install the washers back onto the shaft, put the assy
back onto the faceplate and reattach the shafts nut.  Slide the washers back
onto the dial wheel and make a snug fit.  Then tighten the shaft assy nut and
you should be back in business.

The second part of this problem is a bit more difficult.  The way I do it is to
remove the LMO from the radio.  With the LMO removed and all the dial stuff
removed, look at the LMO from the front and down in the lower left area.  There
is a shaft coming out of the LMO.  It has a collar that is held in place by a
very small allen set screw.  Remove this collar.  Look carefully behind the
collar and you will find 6, interlocking leafs.  Carefully remove them, one at
a time and set them on your bench.  When you have the last one out, start
cleaning them.  I use a small propane torch and remove as much of the embedded
grease as possible.  Then recoat each leaf with a black moly-lube and
reassemble the LMO.  I would only do this if you are having drift with staying
on freq.  The petroelum based lube has lost its lube properties and when the
radio is cold the lube solidifies.  When you turn the radio on, the lube slowly
starts to loosen up and bingo, you have station drift.

Heath devoted a number of pages in the SB manuals just to that dial interface.

Good luck......your mileage may vary.

Ed
Husband of a "Former Ham at Heath"

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