LASER POINTER HOLDER IDEAS - ETX AND OTHERS Last updated: 23 February 2007

Subject:	ETX-125PE Mechanical Assembly Notes
Sent:	Thursday, February 22, 2007 17:27:55
From:	charles c. littell III (chas@littell.org)
Surgery was a success.  Here are some highlights.  I attempted to
photograph features of the ETX-125PE that I have not discovered in other
data on Mike's site.



The finder / LNT assy is secured by ONE TINY SCREW only, with a tab
fitting into the right OTA chassis (not shown.)  The screw hole is
visible here, as is the screw (re-inserted into the body so it didn't
get lost!)



This is pretty important--if you want to pull the finder, use the one
tiny screw, NOT the two under the finder base.  They are not into
threaded holes, but rather have nuts underneath.  Replacing that screw
with a knurled bolt could be an easy way to remove the finder assembly
that prevents the PE model from fitting the Meade hardcase, hmmm.



The OTA is slid to the rear after a fairly forceful spreading of the
rear of the two tube saddles away from the OTA while gentle rearward
force pops the left and right tabs from the slots at the front of the
saddles.  Then five screws may be removed (shown) to separate plastic
from the metal fork assy.



Here is a dramatic difference--the husky-looking drive assy has a worm
gear engagement adjustment.  The same three worm gear base screws must
be loosened, but then the gears are pushed into adjustment by a bolt
(shown, top right of assy.)  Interestingly, this bolt was the ONLY
metric ( Allen ) bolt I found, and an SAE  Allen  wrench will not work. 
I adjusted by tinkering with both base mount screws and adjustment bolt
until the worm gear no longer "spun down" after a speed-9 slew, then
backed off just slightly.  I also took out some of the lateral play on
the worm gear, adjusting large nut at top while holding worm shaft with
needle nose pliers.



I didn't pull the clutch assy apart, but note that the clutch thrust
bushing just hangs on the hub, might be easily lost or overlooked. 
Also, note worm gear engagement adjustment bolt access hole on the
right.



The Az drive was pretty much as expected.  I didn't oberserve any
lateral play on the worm gear, but the engagement did need to be
tightened (three worm gear base screws loosened for this.)  The result
was about 1/16 rev slop on the encoder wheel, pretty good me thinks.  I
have no idea what that big black wheel is...?



Reassembly of the OTA was the only irritating chore.  The finder / LNT
harness was obviously added to an existing design, and I don't see any
perfect route to get it from the hub, along the OTA chassis frame, and
out the access hole.  The photo above (OTA partially back, two inches
from home) shows the harness routed incorrectly out the finder frame tab
slot instead of the larger notch to the rear.  I ended up using tape to
secure the harness to the middle (yes, middle) of the OTA saddle for
assembly.  It actually seems to bind less in the middle, but it still
binds and extreme care must be taken not to mutilate the harness
insulation during reassembly.  Then, the harness binding tends to make
the saddle separate slightly from the OTA, and the tab won't slide into
the slot in the front of the saddle.  Repositioning the harness as
required, a severe talking to, and finally an affectionate hub-to-hub
hug seemed to do the trick. That's all I photographed tonight.  It works
fine in my dining room, it sounds good, and who knows, when I get it
outside it may even work better than it used to. Chas

Charles C. Littell, III
Dayton, OH

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