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Subject: Re:LX-200 focus problems
From: Sam Lattuca
Reply To: mapug@shore.net
Date: Sun Dec 03 00:08:40 1995

Ref:
I found that if I tighten the assembly to the rear cell, the focuser knob
gets very hard to turn. I tried wiggling the focuser and retightening
several times but the result was always the same. Tightening the three
screws all the way causes the focuser to almost lock up.

Tom,
If your focuser will operate the mirror assy when it is backed away from
the rear cell then the focuser is probably working ok. You can always check
the focuser for binding by completely removing it and examining its
operation out of the scope. When you focus you are running a threaded bolt
in and out of the insides of the focuser knob by way of the focuser
plate(has the 3 screws in it) that remains stationary. Since the bolt
travels in and out with the knob rotation the effect is lengthening and
shortening the bolts travel in and out which moves the mirror. You should be
able to tell by holding on to the plate and manually running the focuser
knob from one end to the other. I'd watch to make sure that the action is
smooth and the focus bolt is straight. It's also a
good time to notice that the backlash adjust can be checked easily now.
While holding the focuser plate (3 holes and attaches to rear cell) and
turning the focuser knob, notice that there is a slip clutch action that
occurs between the knob and the plate body, and the plate body and a metal
sleeve. If while holding the focuser plate you can move the knob in and out
any, then the clutch is set for a little backlash. If there is no in and out
play, then the backlash is set snugly. If it is too snug, it will be
difficult to hold on to the plate and turn the knob. In this case it is way
too tight. To adjust, loosen the two hex screws in the focuser knob and
while gripping the metal sleeve on the opposite side with a wrench (snug,
dont clamp), rotate the focuser knob CCW about 1/16 to 1/8 turn. Tighten the
hex set screws and recheck for looseness in and out. I prefer mine to be
just where there is no slop (backlash) but just loose enough to turn freely.
If all that checks out, then there must almost have to be some
binding of the mirror baffle on the optic tube at the end away from the rear
cell. This is presuming that the focuser assy is being seated in squarely
with the mirror assy arm. I suppose that it is possible that some
accumulated debris in the grease could have been forced to one end and piled
up causing some binding when you attempted the re-distribution method. If it
cant be worked out by re-distributing again or no other cause can be found,
I suggest opening it up and doing a re-lube. You wont be sorry with the
results if you go in prepared.
If you would like a disassembly procedure, let me know. Hope this helps.

Sam Lattuca
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"Karma is as karma does!" "What me worry?
--Maharishi Gump-- --Alfred E. Neuman--

Sam Lattuca
lattuca@midwest.net