ETX TECHNICAL TIPS
Last updated: 20 January 2006
Subject: writeup: repair ETX-60/70 focusing knob
Sent: Wednesday, January 18, 2006 21:18:27
From: jacob webb
After searching your site (along with the rest of the web) for info on
how to fix a stuck focusing knob on my ETX-70 I decided to operate on
mine taking pictures along the way. I made a brief writeup with
pictures in html format that you can post freely on your site. I don't
think it looks pretty, but it is useful info on disassembly. Best of
all it worked!
This writeup was made to document my own attempt to repair the focusing
knob on my Meade ETX-70 Telescope. This telescope had not been
used for years, and upon using it one starry night I realized that the
focusing knob was useless. My problem was that the focusing knob
would turn freely without actually moving the focusing barrel.
The only way I found to focus on objects was to move the eye
pieces out from their socket a bit while looking through, then clamping
them. It was obviously jammed, and so I figured I'd try to breath
some life back into this scope.
-Allen key provided with telescope (used to remove focusing knob and horizontal locking lever)
-Larger Allen Key for removing 4 bolts on the back
of the scope (it's still fairly small, but larger than the focus
-Socket Wrench and 1/2 inch drive for removing the nylon locking clamp
-A flat blade and phillips screwdriver
-A clean workspace and plenty of patience.
Figure 1: back of telescope
Step1: Remove the focusing knob using the provided allen key. Put
the knob and locking nut in a safe place (the knob can be removed
without fully removing the nut).
Step 2: Remove the 4 bolts on the back of the scope using the larger
allen key (try a bunch 'till you find a good fit). Put these
bolts in a safe place.
You can almost remove the focusing barrel now, but the rest of the job is more complicated and time consuming.
Step 3: If you have not yet removed your scope from the tripod,
now is the time to do so. Remove the two plastic knobbed screws
from the underside of the tripod. Hold the base of the telescope
firmly and pull away from the tripod base(the large round part, not the
scope itself). Mine took a fair amount of effort due to the
stickiness of the rubber feet on the base.
Step 4: Remove the plastic cover from the bottom of the base (use a flat blade screwdriver)
Step 4: Use the same allen key used on the focusing knob to free
the horizontal locking lever (located by the battery compartment).
You can use the lever to loosen the bolt that is underneath.
Step 5: Remove the bolt.
Step 6: There should be a 3 legged metal bracket on the bottom
side of the base. This can now be removed along with the two
washers. Keep them in order and try not to degrease them.
Now grab your socket wrench and remove the nylon threaded clamp.
The bottom of the base should now be free.
Step 7: It is now time to remove the right arm of the telescope
support. Do so by unscrewing the three screws found above
(opposite to the motor). This is one greasy bit, so try and stay
clean and keep the grease on the parts. Loosen the Left arm if
necessary, but remember that only one of the arms needs to be removed
in order to free the barrel from the base stand. The gears from
the controller port side of the scope (Left arm) might try and
pop out. If they do, keep them in order so you can put them back
Step 8: There are only two screws holding the black plastic onto the
blue barrel now (highlighted in purple above). Remove these
screws with the Phillips screwdriver.
Step 9: Separate the black plastic backing (Cell-Back) from the blue tube.
Mine was really stuck, so I placed the focusing rod on the edge
of a table and pushed down on the black rounded sides. The tube
should now be completely free. Avoid touching the CellBack flip mirror.
Step 10: Separate the two sections of the Blue Tube (separate the
Optical Tube from the Movable Objective Lens Cell). This should
pull the focusing rod inwards because it is attached to the end of the
scope with larger diameter (the movable objective lens cell). I'd
recomend keeping the lens cap on the end of the scope to avoid
scratches or damage. There is a small brass ring clamp that keeps
the rod from protruding too much when bringing the focus to its nearest
setting (thus shortening the barrel length. Take care to guide
this brass ring through the holes in the abs housing. There is
probably a clear plastic ring on the knob side of the brass clamp that
you do not want to lose. This keeps the brass ring from digging into
the ABS on the Cell-Back.
Step 11: Now that the Lens Cell is separate, you can inspect the
threads to make sure they are clean and move freely. Mine looked
rusty, but still had some grease on them. It would probably be a
good idea to degrease this part, and then to relubricate it using
lithium or similar grease. Remember that WD-40 is a degreaser,
not a lubricant. Take extra special care to not touch the optical
lense or to drip anything on it.
I actually left mine how it is (without degreasing and re-lubricating),
but if I had the materials on hand at the time I would have done so.
I think that the main cause of my jammed focusing rod was the
plastic on the Cellback. It just needed to be unstuck, and seems
to work fine now.
TIME TO REASSEMBLE!
Make sure you line up the holes on the right fork arm. There is a
spring inside this arm (the cover has been removed for visibility).
It's easiest to try and point the scope perpendicular to the Base
Housing so that this spring will be under no tension. Note that
there is not and equal 60-60-60 degree spacing on the holes, and that
they must be aligned properly. There is only one right way to fit
That's it, just do the reverse of what you've done and everything
should go back together. You can now focus on objects again!
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Copyright ©2006 Michael L. Weasner / firstname.lastname@example.org
Submittal Copyright © 2006 by the Submitter
URL = http://www.weasner.com/etx/techtips/2006/etx70focusfix.html