ETX-70AT Teardown

More telescope fun. I have an Meade ETX-70AT telescope that I got at a pawn shop for $15. It was missing the battery pack, eyepieces, and the focuser seemed jammed. Since I have eyepieces that fit it, and the focuser seemed like it might be an easy fix, I naturally bought it and brought it home.

I built a 12v battery pack for it, but found the handset connection seemed to be intermittent, and when the handset did come on, it showed a “Motor Unit Failure” error. I opened it up and verified the motors were not bound up and none of the gears appeared to be stripped. Some of the ETX message boards online suggested making sure the encoders were not blocked with grease or other debris, so I checked this as well. While the main circuit board was exposed, I also checked it over, and reflowed some of the solder joints that looked sketchy. Still getting the MUF error after getting the handset to come on. Hmmm.

Giving up on that for the time being, I moved on to the optics, and pulled the primary lens and focusing rod out.

The issue with the focuser turned out to be a little washer on the focusing rod. It is supposed to ride on a step in the rod, but it had gotten pushed over the step and further up the rod. I removed it, and smacked it with a hammer a few times to flatten it back out, and now it sits properly on the step. The focus seems to work, other than the fact that I lost the focusing knob somewhere during all this. It’s just as well, the knob is in a very awkward place, and I am planning to extend it out with a flexible shaft anyway.

While putting the telescope back together, I did some more troubleshooting on the electronics, and found that the MUF error only comes up if the power is on when I fiddle with the handset connection to get it to come on. By wedging the connector with a screwdriver, and then turning the power on, the system boots up normally, and goes into the alignment mode, and then will attempt to seek to whatever object is selected.

Now I just need to work on the focuser extension, and figure out some kind of mount or tripod for it. Oh, and figure out something better than a screwdriver to wedge the handset connection with.