Meade ETX-90 Right Tube Adapter Repair Service (ETX90 RTA Mount) For Sale
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Meade ETX-90 Right Tube Adapter Repair Service (ETX90 RTA Mount):
$45.00
This listing is NOT for a new adapter. Please read the description and ask questions before buying. No refunds.
If you can not tighten the declination (up/down) axis of your Meade ETX telescope mount, and your telescope points down with no recourse, its right tube adapter has broken.This listing is for my right tube adapter repair service. I have engineered a fix for the right tube adapter (RTA), and will repair yours in about 10 days. If repair is not possible, I will provide a full refund. In any case, I will return your RTA to you via the shipping method of your choice. The RTA is the most unreliable component in the ETX family of telescopes. It is poorly engineered and will inevitably fail with use. It has several failure modes, all of which result in inability to point the telescope at desired targets.One of the failure modes is seen the the first picture above. It is caused by tightening the friction clutch of the declination axis in routine use of the telescope. This applies tension to the RTA\'s rotational shaft (the part with the brass insert). Due to poor load distribution throughout the RTA, the shaft eventually fatigues and fractures. The fracture usually occurs where the shaft intersects its base at a right angle, but can occur anywhere along the shaft.Another failure mode occurs due to the use of a small (1/4\") and therefore grossly inadequate threaded insert in the shaft of the RTA. Tightening the friction clutch via the large knob on the side of the fork mount pulls on the insert, with the force transferred to the rest of the RTA via the tiny area between the insert and the shaft. Predictably, it is not unusual for the insert to simply be pulled out of the shaft in normal use.Meade used to charge $175 to repair telescopes in this condition, but they no longer offer even that. So to repair my own RTA (which is in the first picture), I had to engineer a repair. Since I really like my ETX-90EC optically, I wanted the repair to last forever. My repaired RTA is in the 2nd through 5th pictures above. It is now much much stronger than the original part, and will never again fail in the same way. The key to the repair is a custom-made brass insert which extends from the location of the original tiny insert, down the entire length of the shaft, and into the base of the shaft (6th picture). The segment of the insert which extends into the base is further anchored by a rock-hard composite material, and is secured by a screw and washer (7th and 8th pictures).The long brass insert acts as a spine which helps the RTA shaft resist bending loads, especially since it is anchored in a very tough composite material. But more importantly, it converts tension along the shaft to compression of the composite material against the base, eliminating any possibility that the shaft will fracture due to tension. Furthermore, unlike the original insert, there is no chance the long insert could be pulled out since it is secured from behind the base of the shaft with a screw and washer.Upon payment, I will provide instructions for shipping the RTA to me. As I mentioned above, my turnaround time for this repair is approximately 10 days.
Here are the instructions for removing the RTA:Please first remove the optical tube from the mount. Do this by removing the 2 socket head bolts on both the right and left tube adapters. Then gently spread the forks outward while pulling the optical tube rearward (toward the eyepiece). You may need another set of hands for assistance.Now completely unscrew the declination clutch knob, which sits over the dial with angular markings on the right fork. Then simply pull gently on the right tube adapter to remove it from the fork.
