ETX TECHNICAL TIPS Last updated: 31 December 2004

ETX-60AT: Motor Won't Turn in Horizontal / Azimuth Direction

Sent:	Sunday, December 26, 2004 08:22:40
From:	aek@pumpkininc.com (aek@pumpkininc.com)
My father-in-law bought an ETX-60AT over a year ago, and hardly used it.

Yesterday, I found it in a closet, and thought it would be nice for my
two girls to use.  Unfortunately, the horizontal / azimuth motor doesn't
seem to engage -- just makes some (not unpleasant) noises. The vertical
/ altitude motor works fine with the Autostar.

I popped the lower cover off, and it looks to me like the horizontal
lock / clutch simply doesn't engage tightly enough for the motor to turn
the 'scope.

Since it's out of warranty, I thought I'd give it a try to fix it
myself. However, it's not too obvious to me how to get access to the
motor, nor to adjust the clutch./ Must I remove the horizontyal lock
lever? 'Cause the screws under the little rubber feet appear to only
hold the internal metal plate / weight in place.

Any tips / help on disassembly are appreciated.

--Andrew

And:

Thanks -- that looks promising.

Now I gotta go find the Allen wrench! Any idea what size it is if I
can't find the original? 1/16?

--Andrew

And:

Found the Allen key -- cute, how they do the horizontal locking via a
simple hex-head bolt.

Anyway, that had no effect. I.e. doesn't matter how tightly the
horizontal lock is set -- won't turn, but motor is running.

I suspect something inside is loose / has follen off ...

Regards,

--Andrew

And an update:

Thanks for your help and website.

It turns out that the plastic "tensioner spring" that pushes the
horizontal motor's worm gear against the ring gear had broken, so the
horizontal motor was no longer able to turn the base.

So, after disassembling the unit (and note that the white plastic "nut"
did not shear off as per the link you gave me -- I was able to simply
unscrew it), I drilled and tapped (8-32) the center upright of the
casting to accept a spring-loaded pin, VLIER P/N SSMD-51A. I also
drilled a small access hole in the base (not shown) at the correct
height so that I could adjust the pin for appropriate tension once
everything was assembled.

I've attached two pics to show the mod -- perhaps some of your website
visitors may find them useful.

The first pic shows the spring-loaded pin in its initial position -- I
screwed it in a couple of turns once the base was attached, to achieve
proper tension of the work gear against the ring gear.






Regards,

 ______________________________________
  Andrew E. Kalman, Ph.D.   aek@pumpkininc.com

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