Sent: Friday, October 1, 2010 11:54:11 From: Paul Bonneau (firstname.lastname@example.org) I have the plain ETX-90 with the manual dec adjustment. On mine, the dec "slow-motion" adjuster was extremely stiff; so stiff that I worried I would not be able to detect the end of its movement and thus break something. The first photo shows what the mechanism looks like after taking things apart (the procedure is the same as shown in other tech tips). The two aluminum knobs turn the screw, and an aluminum button moves on the screw, and the plastic "yoke" (I guess you'd call it) that moves the declination has a forked end that slides in a slot on the button. Essentially all of the friction is where the knobs contact the plastic arm at the end. In my case the yolk also gripped the button too firmly, I thought, so I widened the slot in the yolk a tiny bit with sandpaper (one must be very careful not to remove too much material, thus introducing slop into the mechanism). Photo 2 shows where I have flipped the button over and I'm checking the grip of the slot on the button. Once I got it where it slides, but without gripping the button too hard, I stopped. I cleaned it and put a little grease there so it could slide on the button while still gripping it. Photo 3 just shows the slot on the end of the yolk that I was (slightly) widening. I noticed the button had some slop on the screw; the tap used on the button must have been too large. I attempted to squeeze that end of the button with a vice-grip, hoping to deform it enough to grasp the screw without slop, but I was unsuccessful in that. I wanted to take the whole mechanism apart but never saw how to get the knobs off. I thought about greasing the screw with very heavy grease to fill up the slop, but didn't do that. Photo 4 shows my hand squeezing the plastic arm. When this is done, the knobs rotate freely. I watched the action of the screw while rotating the knobs and detected a bend in the screw. I put the bend at the top of its arc, and then pressed down on the center of the screw, straightening it somewhat, at least as much as I could detect. This straightening removed some of the on-and-off friction in the rotation of the screw knobs, making it more even. I had some teflon-based lubricating oil, and put a drop into each point where the knobs contacted the arm, while squeezing the arm to make room for the oil to flow into the joint. After doing this, and after reassembling, the knobs rotated just about perfectly - with enough friction to hold, but not so much that it was difficult to turn. I believe there is supposed to be some friction in this mechanism, because there is no lock for it (the "declination lock" does not lock the mechanism). While the thing was still open, I moved the button to the center of its travel, then with a knife made a little notch where the declination lock was. This allows me to find the center of travel without having to run the thing to the end and then going back 50 turns as the manual suggests! When reassembling I added some plumber's teflon tape, as suggested elsewhere here, around the declination pivot pins. I used 3 turns. Seemed to help reduce slop in that joint. In the 4 screws holding the OTA to the fork mount, some ham-handed assembler had broken through the plastic on one screw and cracked a couple of others. I don't believe these screws should be very tight. I suppose I will have to see if I can pry a couple of these plastic pieces out of Meade. The design is very poor here. That's it!
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