Last updated: 3 March 2002
Sent: Friday, March 1, 2002 16:18:27 From: email@example.com (Paul J. Boudreaux) I've had my ETX125 for nearly two years with little trouble until the past few months. I noticed that it had problems in the RA and the Dec lock showed some up/down wobble. I have never had the courage to open this telescope, but after reading the many references on your site, (Jordan Blessing's ETX/EC Tune up, ETX/DS Technical Tips, Bob's LX200 Web Page :Supercharge your ETX, and many of Dr. Clay Sherrod's web postings) I decided to find the problem. After removing the OTA, and the Dec knob and clutch, I tried to remove the inner side panel by taking out the five screws. To my surprise, it would not come off! After carefully prying it around the edges I found that it had been glued down along the bottom edge. When I removed the panel, the inside of the side arm appeared to be covered in large black particles about the size of coffee ground. At first I could not locate the source of these particles, then I saw (by comparing photos posted on your site and others) that the two Backlash Adjustment screws in the base of the worm gear housing were just sticking out into thin air. There was no trace of the plastic tabs that they were supposed to press against. In addition, one of the three sheet metal screws holding the worm gear assembly was just hanging in air with nothing to thread into. The second screw in the worm gear assembly was loose while the third screw was still tight and held the worm gear housing in place. Apparantly the plastic base that these sheet metal screws tapped into had shattered and that allowed the worm gear assembly ro rock against the two plastic tabs destroying them in the process. To repair the damage I first reconstructed the broken and partially missing tabs by using "scotch tape" and children's modeling clay to form a sealed dam to form each tab. A flat edge piece of wood acted as a form to insure that both tabs that would be reconstructed would be planar and parallel to the old tabs positions. I thought the real problem would be to determine the correct height that the worm gear housing had to be away from the side wall. Then I observed that although the original sheet metal screws attached into plastic cylinders that also could act as spacers, they realy did not matter because the metal back plate has three metal tabs that actually support the worm gear housing at the proper height. That enabled me to replace the sheet metal screws completely because there were three 4-40 body holes in the base plate where the plastic sheet metal screws had attached. I used three 4-40 stainless steel pan head bolts to replace these screws. Pan head bolts are required instead of round head bolts because they ensure that there will be clearance between the bolt head and the Aluminium Dec wheel cover and lock Knob on the Dec clutch. The pan heads are shallower than the four notch tabs that press against the inside of the Dec wheel outer hub. A lock washer and a 4-40 lock nut completed the repair of the worm gear housing mount. Following instructions from your site, I adjusted the gear mesh with the adjusting screws, now that there were tabs for them to press on. Back in business! No more Dec wobble - things are tight as a drum once again. Thanks, Mike! Without the help of your site and its many contributors, I would never have ventured into the world of ETX tune up and repair! I attached a JPEG image of the epoxy tab repairs. Paul Boudreaux
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