ETX TECHNICAL TIPS Last updated: 28 October 2004

Repairing ETX Fork Adapter

Subject:	ETX-90 down
Sent:	Thursday, October 21, 2004 11:39:37
From:	Rafael Falquina (rfalquina@yahoo.es)
unfortunately, my (less than 6 months old) ETX-90 fell down to the
ground. I was not present but apparently the OTA didn't touch the floor.
The scope was attached to the 884 tripod and only the base hitted the
floor. The optics look good but the OTA suffered a torque and it is now
out of its correct place between the fork arms. Specifically, it is not
in direct contact with the fork arm which holds the alt scale. I'm
attaching a few pics to show you better what happened. It doesn't look
like anything is broken, more like it is out of place. My question is,
how can I check that no parts are broken and put it in place again ?
Will I void my warranty ?


 
 



I haven't switched on the scope and I don't want to do it until I hear
your response.

Thanks in advance for your help and for your great site.
Rafael.

From:	P. Clay Sherrod (drclay@tcworks.net)
It is very possible that the hold-down tabs inside each or one of the
OTA adapters (the swing arms) has sheared from the fall; the only way to
tell is to remove the OTA from the arms by removing the four hex head
screws and examining inside the round part of the OTA adapter and look
for breakage on the flat tab....I suspect that one of them is broken.

Clay
--------------------
Dr. P. Clay Sherrod
Arkansas Sky Observatory
Harvard MPC H41 (Petit Jean Mountain)
Harvard MPC H43 (Conway)
http://www.arksky.org/

From:	Richard Seymour (rseymour@wolfenet.com)
If the telescope fell to the ground because of a failure of
the Meade tripod, the damage may be covered by their warranty.

Four years ago some of the Meade tripods would slowly collapse
while the telescope was not in use.  Since it was a Meade 
tripod which caused the damage, Meade replaced (or repaired)
both the tripod and the telescope.

Contact your dealer, or Meade Europe.

good luck
--Dick

Thanks you all for your help.
 
I'm afraid that the tripod was OK, but my wife was not careful enough
when moving it.

Following your suggestions, I'll try to remove the OTA from the fork
arms to see what happened, but before that I have to face a (sadly
expected) problem. There wasn't any hexagonal key of the appropriate
size included with the scope, and it seems to be of a standard size in
the U.S. but not here, probably a tenth of an inch. During the weekend I
visited a few hardware stores with no results. I'm proud that this is
the same kind of problem they had with Mars Climate Orbiter (just
kidding, living with two sets of units is sometimes a nigthmare)

Now I'm thinking of buying a keys kit from Amazon UK. If that's not
possible I'll have to wait until my (or one of my job fellows) next trip
to the U.S.
 
Regards.

Best of luck to you on this project....I suspect you can get it fixed
without much trouble and let's hope that the tab on the fork adapter is
not broken....
 
Clay
--------------------
Dr. P. Clay Sherrod
Arkansas Sky Observatory
Harvard MPC H41 (Petit Jean Mountain)
Harvard MPC H43 (Conway)
http://www.arksky.org/

From:	Rafael Falquina (rfalquina@yahoo.es)
finally it wasn't so difficult to find the Allen keys in inches. After
removing the OTA from the arms I found that one of the plastic tabs on
the round edge of the OTA rear cell is broken, the one corresponding to
the arm with the dec clamp (see the picture). I put the OTA back between
the fork arms but there is a lot of play in that arm and it doesn't seem
safe to use the scope in this condition. 




Can I do anything to repair it? 
Thanks again.

From:	Rafael Falquina (rfalquina@yahoo.es)
not sure that a new "Right Tube Adapter" will do it. The broken tab was
on the rim of the rear plastic cell of the OTA (it clips in the adapter,
but the adapter itself looks undamaged). Or maybe I'm confusing terms,
my "hardware" english is limited. Please, could you take a fresh look at
my latest picture and confirm that we are talking about the same broken
tab ?
 
Thanks.
Rafael.

"P. Clay Sherrod" (drclay@tcworks.net) wrote:
>Hello....
>That is what I thought had happened.  There is absolutely no way to repair this 
>since the tab is so thin and fragile; the only thing you can do is to call or 
>write Meade and ask for a "Right Tube Adapter" for the ETX 90; they very likely 
>will send one out to you at no charge.
>Best of luck on this!
> 
>Clay

From:	P. Clay Sherrod (drclay@tcworks.net)
Ouch, ouch.  You are correct.  That is much more serious.  However I do
have a fix if you are patient and take your time with steady hands. 
Take the OTA and position it where you can drill two tiny holes in LINE
with the optical axis, into the small ridge where the tab broke off. 
Put those holes where they will fit "inside" the short span that was
covered by the original tab.  Drill ONLY about 1/8" into the plastic and
no deeper and take care to NOT drill at an angle into the tube....very
hard to do, but I do it every week so it can be done.

Once the two holes are there, cut two tiny rods of steel (not aluminum
or soft metal) to fit into them tightly and extrude like pins about 1/4"
outward....these will actually take the place of the flat tab that has
broken off and will engage into the right Tube Adapter.  The pins can be
made from a LARGE paperclip or my preference is to cut stainless steel
drapery hooks and use the pointed end to insert into the drilled
holes....tap lightly with a very small tool using a block of wood to
buffer the blow against the tip of the pins.

It is a good idea to put two drops of RED Locktite (or other similar
"superglue") into the hole before tapping in the pins...however make
sure that you work quickly if you do and only glue and insert ONE pin at
a time as the glue will harden quickly.

If the OTA has trouble engaging the new pin system, you likely have made
them too long, or they perhaps are angled too far out from the actual
axis of the tube assembly.

Best of luck....t'aint easy.
 
Dr. Clay
--------------------
Arkansas Sky Observatory
Harvard MPC H41 (Petit Jean Mountain)
Harvard MPC H43 (Conway)
http://www.arksky.org/

What do you use to drill the holes ? None of my friends is a dentist :-)
 
Grateful Rafael.

A very, very tiny drill bit....(no joking here....).  I use a 1/64 or
1/32 inch bit....it is a lot easier if you use a Dremel to do this, and
those bits are quite common for that tool!
 
Dr. Clay

Return to the top of this page.

Go back to the Tech Tips page.

Go back to the ETX Home Page.