Grinding the counterweight rod nut on a Celestron AVX mount

On a Celestron AVX mount, the counterweight rod nut was grinding on the DE axis. This symptom appears frequently in the forums, so I investigated it.

My suspicion was that the DE axis was no longer running smoothly or that its clamping was no longer optimal.

To test this, the DE axis was completely disassembled:

First, the declination axis is separated from the right ascension axis. This axis is held in place with two screws (5mm Allen key). These can be seen on the collecting tray in the image above.

The head is then removed using the prism clamp (5mm Allen key).

 

The first part of the DE axis becomes visible.

 

Please pay attention to the small transparent slide that rests on the worm gear:

 

Before you try to loosen the lock washer on the other side (where the counterweight rod is screwed in) with brute force: there are two grub screws at a 180° angle to each other, which are visible in the small opening (on the right in the picture).

 

Only now can you loosen the lock washer:

 

Spoiler alert: this clamping washer was the problem when grinding the nut: it wasn't seated correctly.

Removing the motor:

4 Phillips screws on one side (top).

 

The engine becomes visible.

 

Loosen the two Phillips screws at the bottom.

The motor is held in place by four Allen screws (size 5):
 

This is what it looks like disassembled:

 

If the worm gear has been removed:

 

Please pay attention to the second transparent plastic ring that sits on the other side of the worm gear.


 

There's still a white Teflon ring in the housing...

After re-greasing the axle and carefully adjusting the lock nut, the problem disappeared.

Reassembly in reverse order, of course.

Yours, Karsten