Repairing and Tuning Celestron Evolution Mount

[geyes30]

I bought a Celestron Evolution 6 off the Buy and Sell section here, and it's had a fraught life, to say the least. It started with a busted internal battery, followed by a complete burn-out of the main board. Recently, I was able to obtain a replacement board for cheap (more on that next time), and having used many other mounts since the Evolution died 15 months ago, I was aware of play in the gear meshing. Now, the Evolution uses worm gears to drive the two axes, and should in theory have minimal backlash. However, in my copy, the Azimuth backlash was so bad that even maxing out the anti-backlash setting (99) was unable to clear it. So I took it upon myself to repair the mount.

Having replaced the board and played with the insides of the mount many times, I was very comfortable with taking it apart. All it takes is a set of metric Allen or Hex keys, and you can remove the knurled clutch ring (see first image below), as well as the whole plate that covers the guts of the mount (second image).

Untitled by Cyrus Beh, on Flickr

Untitled by Cyrus Beh, on Flickr

Next, you will see that the worm gear is driven by two small spurs and meshes with a very large spur gear, as below:

Untitled by Cyrus Beh, on Flickr

Activating the motor this way will show you how bad the backlash is (if the small spurs turn a lot before the largest spur gear does, as was the case for my mount, we have a problem). You can also test the meshing by loosening the clutch, and jiggling the gear. If there is a lot of play, you can loosen the motor by unscrewing two screws holding it down.

Untitled by Cyrus Beh, on Flickr

The screws sit in the slotted holes, which you can then move forward and backward to improve the meshing. Make sure to test the movement before tightening. It will be VERY bad if the gears bind! You can potentially ruin the motor.

After the adjustment (all of ten mins) the mount is now super responsive. Anti backlash setting of 10-15 is all that's needed!

[Airconvent]

Always great that someone can repair any mechanical equipment! Thanks for sharing and enjoy your scope..It's a good one!