ETX TECHNICAL TIPS Last updated: 25 June 2001

ETX-90RA "sticky" Right Ascension movement fix

Sent:	Sunday, June 24, 2001 15:59:25
From:	sherrodc@ipa.net (Clay Sherrod)
>Good Doctor:
>
>I have an ETX 90RA that has a pretty stiff touch on the RA knob when
>making adjustments. It turns, but hits "sticky" spots that require
>enough force as to make movement quite awkward.
>
>Any speculation as to what might be the cause of this? More
>importantly, is this something that can be fixed without being
>shipped to the factory?
>
>Suggestions appreciated.

The problem is in the locking clutch that the lever is attached to.  It
has a "high point" somewhere on the small disk that pushes against the
drive gear when the clamp is tightened.

I have a suggestion that will likely help without you having to get
inside the telescope NOR having to send it back to Meade.  On the ETX 90
RA, most clutch irregularities can be smoothed out by doing the
following:

1) first unclamp as loose as it will go in RA and then rotate the
assembly 180 degrees in one direction and then the other about three
times both directions;

2) very gently tighten just a bit the locking lever until you can feel a
tiny bit of more resistence when you now attempt to rotate just like
before; with the clamping lever engaged in such a position, repeat the
rotation noted in 1) above;

3) now tighten down until the RA axis will move, but with some degree of
pressure from you in either direction; again, rotate 3 times 180 degrees
in both directions;

4) OKAY...now unclamp to the position in step 2) above (slight pressure)
and TURN THE SLOW MOTION KNOB until you reach those points where you are
experiencing the resistence; stop there;

5) now firmly clamp down the locking lever until the scope is tight in
RA but you can STILL move by hand and override the clutch; work the axis
back and forth ONE HOUR of right ascension by HAND....NOT by the knob;

6) move the scope back to the rough spots and lock onto them dead center
and clamp even a bit more;  NOW turn the knob 1/2 turn clockwise and
then counterclockwise several times.

7)  do the same steps at every point you feel this rubbing effect.

Over time that will re-seat the clutch relative to the drive gear.

Good luck!

Clay Sherrod

Return to the top of this page.

Go back to the Tech Tips page.

Go back to the ETX Home Page.