Sunday, August 18, 2013

reviewed the damage

Thierry just left.

He arrived on time with his Meade LX200 GPS in a JMI case. We hauled it up to the kitchen table. He was keen to start. So we do the analyses together. He brought some Allen keys. I fetched my set from the garage along with my halogen work lights.

We disassembled the right fork and focusing controls, photo documenting along the way. We started by removing the facia on the right fork, so to look at the Dec/Alt Slow Motion control.

We found a cork ring, torn, behind the clutch plate, tangled up in the axis. This would normal sit on the track of the clutch and serve as an interface between the large motor gear and the clutch. We gentled removed the ring. It was covered in grease.

The thin smooth metal shaft to the Dec motor was clearly bent. But there did not appear to be damage elsewhere. The transmission looked fine. I did note that the suspension spring mount and seat did not appear to be in alignment, but it still functioned correctly.

We turned the mirror shift locking knob. There seemed to be no resistance or tension. It was spinning freely. Normally it would tighten snugly and then loosen and never run free. We removed the knob assembly. The end plate was clearly bent. Flanged out in two places, in fact.

Now we could see inside the rear cell. The large wheel with teeth, which operates the collet, was some distance way. Far enough that the lock gear was not engaged. That explained why we were not feeling any resistance. The mirror (and gear) had moved toward the corrector, far enough, so that the lock and gear were not touching. It looked like the mirror assembly had been violently moved forward making the gear "hop" over the end plate.

We turned the locking gear by hand and found the damaged area. It was deformed, bent toward the front of the OTA.

Turned the after market focus knob. Looking through the lock port, we could see the mirror move a little bit. And it really only worked one way. So we removed the focuser assembly. Oh dear. Focus rod was badly bent. There's some minor damage to the plastic widget at the end.

There was also quite a lot of scaring on the (soft) brass focus knob shaft. Nothing that will affect operations. 

Then we looked into the focus port. We could see the focus yoke on the back of the mirror. And, sadly, the pin at the end of the yoke, also bent.

Clearly a lot of damage. A half-dozen or so parts to be replaced or repaired. We considered the next steps. I really wanted to see what was going on in the mirror cell but Thierry was a little reluctant to proceed. We decided to leave opening the OTA for another day.

We then tested the electronics. Everything seemed fine. We did a simulated alignment. Slewed to objects. It looked like it was performing fine.

Then, pushing on the mirror directly, we brought the OTA to focus, looking at a roof line down the street. The optics seemed OK.

I committed to sourcing or replacing parts, conducting research, and getting him up and running.

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