TECHNICAL TIPS Last updated: 12 February 2002

Problem with new style ETX-125, or How to Ruin a New Telescope

Sent:	Sunday, February 10, 2002 0:58:22
From:	bob.adair@worldnet.att.net (Bob Adair)
I just purchased one of the new style ETX-125s, and I've run in to a
fairly serious problem (mostly of my own making).  When I received the
scope, I noticed that the RA clutch would not disengage, regardless of
the position of the locking lever.  The lever would seem to behave
normally, but it would have no effect - the RA drive motor was fully
engaged even with the lever in the unlocked position.

Since I had returned a previous 125 because of multiple problems, and
since the optics on this unit seemed pretty good and it was the new
improved version as well (the last one wasnt), I decided to try to
disassemble the clutch to see if I could fix it myself.

The problem that I ran in to is that the new style RA clutch seems to be
of a completely different design than the older clutch, and in the
process of trying to disassemble it I turned the adjustment screw too
far and severed the dec. drive wires that run through the channel in it.
There is plenty of slack in the wires going to the arm, so splicing them
probably wouldnt be a problem.  The problem is:

1) The clutch still seems to be permanently engaged, even with the bolt
out, and I have no idea how to fix it.

2) if I splice the wires or snake new wires through, it isnt obvious how
I can get the bolt back in without severing the wires again, since it
needs to thread in to a ring at the bottom that has tabs which engage
some sort of sleeve the bolt goes through which prevent the ring from
turning.

Does anyone have any suggestions, either about how fix or reassemble the
RA clutch, or how to disassemble the top part of the base so I can
thread the wires through the bolt after it has been re-inserted and
threaded through the ring at the base of the clutch/bearing assembly?

Ive rebuilt devices ranging from mini-computers to V8 engines before
without much in the way of assistance, but this telescope already has me
looking and feeling like a complete idiot. :-)

My advice to anyone else with a new style 125 would be: do NOT attempt
to adjust or otherwise mess with the RA clutch.


Thanks,

- Bob

P.S. - For everybody's information and/or amusement, Ive included some
pictures of the new revision 125.  It appears to be a much better design
than the older versions.


 

From:	sherrodc@ipa.net (Clay Sherrod)
This damage is the ultimate that can be done to the ETX 125....

1) First of all there was nothing wrong with the RA clutch; they all
have a certain amount of resistance and this is perfectly normal; most
ETX 125's run in RA even with the clamp fully disengaged which is not a
problem.  The clamp merely holds the scope firm to the drive gear and it
does not put excessive wear on the system if it drags...it really should
have been left as is.

2) It is correct that you CANNOT and SHOULD NOT attempt any clutch
adjustment with the new models unless you are prepared to have exactly
this happen....those sheared DEC wires are the ultimate in repair. 
There is a technique involved in working on/removing that clutch that is
NOT something that should be done by the owner.  It involves positioning
the telescopes azimuth axis exactly at a set point and subsequently very
systematically loosening (NEVER removing) the center bolt to access the
clutch.  This repair/modification should not be attempted by any ETX
owners for any reason.

3) at this point, with the damage being done, I strongly suggest that
the owner admit that - although adept at rebuilding car engines and
computers - this telescope has a method to its madness and it has him
beat.  This scope needs to go back to Meade with a full explanation of
what happened so that they can fix it properly - AND fix the clutch at
the same time!

My thinking is that this repair will be done very graciously by Meade,
albeit not particularly on an expeditiously rapid pace, for the flat fee
of $75.

Clay

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