Thanks for the post. I have completed the tweaking of my RA drive. One
thing that everyone should be aware of is that it is not necessary to
remover the mother board on the 12" so the site and other info doesn't need
to be re-entered. In fact the flex in the hinge plate can be adjusted
without removing the drive from the scope. It is easier to adjust if you
remove the from plugin panel but not necessary. On mine I had to loosen a
small board to gain access to the adjustment screw. One thing that is
extremely important is to mark the encoder mask very well THIS IS A VERY
PRECISE PLACEMENT. It took me 7 tries to get it back right and I had it
marked. I will re-post after I have a chance to see if it has helped.
Thanks to all who responded.
Doug Schmutz

----------
> Subject: Re: [M]: RA trouble LX200 12"
> Date: Saturday, March 28, 1998 1:25 AM
>
> Doug...
>
> >Anyone with experience with the RA drive removal?
> --------------------------------------------------------------------
> Yep...just did that Valentine's Day this year.
> (I see several responses already but one more ain't gonna hurt)
>
> Removal and reinstallation of the 'goodies' is not difficult---BUT
> the really tricky part(s) deal with the gearbox/hinge assy--STRONGLY
> recommend you read Doc G's description/suggestions/comments on the
> Dec motor at his website (I hard copied those pages).
>
> Once you've got the OTA/Fork/base off the mount, disengage the
> Dec lock and RA lock and lay the unit on a padded surface with the
> base underside at a comfortable working level--control panel front
> facing up and something on either side (base) to keep it from
> rotating on you--more for convenience of working than absolute
> necessity (unless you're a contortionist).
>
> Adjacent to the all-thread input hole are two allen-head screws--these
you
> will remove first (the two larger allen-head screws slightly
> above those two smaller ones are not removed.) The outer perimeter
> screws are next removed and the base cover-sheet-metal can now be
> removed. Note the white "grease" on the inside of the cover-plate-
> DO NOT wipe off--this grease aids transfer contact between the power
> transistors and cover-plate which provides additional heat-sink
> surface area.
>
> You now have an open/exposed innards of the base assy--I took a
> Polaroid pix of this (I forget things easily)--note the plastic
> cable connectors on the M/B--be careful when you attempt removal--
> the plastic spring-locks on the sides of the connectors are hard to
> see but must be released before the connectors can be removed.
>
> Next comes M/B removal--note carefully where the 4 mounting screws
> are located--there are 6 holes but only 4 screws--also, when the
> M/B is lifted out, check immediately the backside to note where the
> little plastic insulator/washers are--there should be a plastic
> insulator/washer for each screw-hole ( 4 ). These, if loose, need
> to be glued back in place so they'll be there when you reassemble.
>
> The wide ribbon-cable can be flipped up and held out of the way
> with a piece of masking tape--careful it doesn't pull loose and
> slap you in the face.
>
> You should now have a clear unobstructed view of the
> RA gearbox/hingeplate assy. I did not remove the individual wire
> cables from the RA gearbox unit---next, note there two allen screws
> holding the RA gearbox/hingeplate assy to the top of the base...
> the screw holes are elongated allowing a sliding-provision for the
> assembly which in-turn affects tooth engagement and optimal
> worm/worm gear engagement. Before loosening/removing the assy, note
> precisely the action of the hingeplate--move it up and note how that
little
> _hidden_ spring pushes the worm back down to fully engage
> the worm gear. Once you're satisfied with your understanding, you
> can remove the two allen-head screws (Doc G suggests a l-o-n-g handle
> allen wrench and I wish I had caught that initially--I didn't--and
> as a result, I 'fought' myself until I got smart and let my 12-year
> old grandson do the operation--my big, clumsy fingers!!
>
> Once you do what you intended to do with the RA gearbox/hingeplate
> assy, reinstallation is a straightforward reversal of that simple
> removal.
>
> The remainder of this msg will be simply excerpts from others who
> were kind enough to send along their suggestions....needless to
> say, READ EVERYTHING THRU FROM START TO FINISH BEFORE BEGINNING.
> -------------------------------------------------------------------
> FROM DOC G:
>
> >Yes, I have taken several of these things apart. You need to be a bit
> >careful but there are no traps built in to the control base.
> >
> >Besure you remove the screws near the central bolt hole and then the
> >screws at the edge of the bottom plate. The central screws hold the
> >heatsinks for the
> >power transistors to the base plate which acts as a heat sink.
> >Do not wipe off the white grease since it is part of the heat
> >sinking contact between the transistor casees and the base plate.
> >Then unplug the obvious plugs and unscrew the circuit board.
> >This all comes apart rather easily.
> >
> >Now you will see the RA drive. Surprise!! it is just like the dec
>drive.
> You get two micro drives for the price of one. The only >difference is
> that the RA drive has a little magnetic detector to
> >tell the computer where the worm is.
> >This is for the PEC drive synchronization.
> >
> >Mechanical problems are exactly the same as for the dec drive.
> >Fix it in the same way by tightening the end play screw which
> >may be the problem. also you can tighten up the slop in the
> >platform motion a bit just as for the dec drive. If the problem
> >is a loose gear within the gear box, and I hope not for
> >your sake, a rebuild of the RA drive, just like for the dec drive
> >might be necessary.
> >
> >Good luck -- Doc G
> ----------------------------------------------------------------------
>
> >From Peter Eichenberger......
>
> >Does the RA play show up without applying force
> >in excess of what the normal scope weight would apply?
> >If not, then this is correct operation.
> >There is a spring in the RA drive that it designed to
> >take up the slack in the gears. Normally, this is
> >stiff enough so that the scope always rides on the
> >same side of the slop; hence no backlash (from that source).
> >
> >-Peter Eichenberger
> -----------------------------------------------------------------------
> From Paul Goelz...
>
> >I generally sit out these drive discussions...... there are a lot
> >of very competant folks out there and you don't need my additional
>input.
> >
> >But in this case, I thought a little clarification/description might
> >help.
> >
> >The motor and gearbox and worm all are a single unit, hinged so that
> >the worm can move in and out relative to the main gear. There is a
> >spring that presses the worm (and motor and gearbox) against the main
> >gear, eliminating backlash. The hinge that the motor/gearbox/worm
> >pivot on consists of two screws that can be adjusted so that there is
> >little or no end float (side to side motion). The idea is to adjust
> >out any end float yet have the pivot still be capable of free movement.
> >
> >With this understood, the possibilities for RA slop are: end float in
>the
> pivot hinge (most likely), loose fasteners in the RA assembly, end >float
> in the worm gear shaft, loose or missing spring, or main gear >loose on
the
> fork.
> >
> >Like John said, dissassemble to reveal the RA drive and gears, lock
> >the clutch and move the forks and see what moves. It should become
>clear
> right away where the problem is. Mine has no slop at all.
> >
> >Hope this helps!
> >
> >Paul Goelz
> -------------------------------------------------------------------
>
> Lastly, make notes, make drawings, don't be 'afraid' of it--
> It "ain't" no big deal---just be careful and be aware that there
> is help around "here"----and let us know how it went....
>
> Hope this helps,
> Gene Ducote (Charleston, SC)

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