4 replies to this topic

[Blitzkriegin]

Hi Everyone,

 

I've got a Meade 628 that has some slop in the RA Axis.  I am pretty sure the telescope is balanced correctly, but the problem is when I try to target an object.  I let go of the scope, and the ra axis slides just a little bit before it stops (it slides the same amount every time).  So if I point at Jupiter, I have to over compensate and move past Jupiter on the ra axis, and then let go and it will slide just a little and jupiter will then stay in the frame.  So the ra clutch stops, it just has a little bit of "give" before it will stop.  Also, this only happens when moving in one direction on the ra axis.  If I move one of the directions along the axis, it will stay put immediately, but if I move the other direction along the axis, it has that little bit of slip before stopping.

 

I'm told this could be Backlash in the motor drive.  I've opened the motor box but there's not many screws that can be adjusted, and everything I have tried does not seem to affect the backlash.  Do these pictures show where the adjustments need to be made to fix the slop/backlash?  Any help would be much appreciated!  Thank you everyone!

 

 

[YourNotSirius]

From what I can see in the second photo there is a gap between the worm wheel and the worm gear. The mesh is loose and that is likely where your problem lays. You should also check to see if the worm gear is sliding back and forth in the bearing housing. That can be corrected by adjusting the stop collar at the end of the worm shaft. The photos aren't clear enough for any further analysis. However, that is 99-44/100 the location of your repeatable gear slop. Just watch the gears as you move the RA shaft back and forth and you will see where the problem is located.

 

FWIW

 

Q

[Blitzkriegin]

From what I can see in the second photo there is a gap between the worm wheel and the worm gear. The mesh is loose and that is likely where your problem lays. You should also check to see if the worm gear is sliding back and forth in the bearing housing. That can be corrected by adjusting the stop collar at the end of the worm shaft. The photos aren't clear enough for any further analysis. However, that is 99-44/100 the location of your repeatable gear slop. Just watch the gears as you move the RA shaft back and forth and you will see where the problem is located.

 

FWIW

 

Q

The worm gear is sliding back and forth in the bearing housing as I shift the RA shaft back and forth.  I adjusted the screw (circled in red) and it eliminated the slop.  The axis is much tougher to move, but it does seem to have fixed the problem.  Was that the correct way to fix it?

 

[sellsea]

According to the instruction manual, the screw circled above is the "worm backlash adjustment screw".  Unfortunately, these instructions do not discuss how to adjust this.  But the manual does mention adjusting the "worm block", into which the "worm backlash adjustment screw" is threaded.  It says that in order to adjust the worm block, loosen the two screws on the opposite side of the backing plate, then achieve minimal clearance between the worm and gear teeth to prevent binding, then retighten the two screws.  In summary, I do not know if the "worm backlash adjustment screw" is used in conjunction with the "worm block" adjustment.

[deSitter]

Typically the way this works - a nut fastens the worm gear into the worm block. This has to be adjusted until the worm gear does not move back and forth along its axis. If you go too far the gear will bind in its bearings. So the best idea is to remove the entire worm block so you can adjust this while manipulating it. Get it too tight, then release it until you can rotate it easily with a finger tip.

 

There may still be some slop at the end - the way to deal with this is to unbalance the scope enough so that the clock drive work uphill so to speak, and the slop is automatically taken out.

 

-drl