Rowan belt mod issue

[Coco]

I did the Rowan belt mod last year on my NEQ6, since then Ive only used the mount 3 times and that was in the West without issue and with superb flat guide graph, but recently I've been trying to image M51 NW and I'm having a guide problem but only in dec, the Dec line can't hold onto the guide star, it dives off the graph, I am using a short 135mm old camera lens as a guide scope but this did not have an issue before the mod, today I'm going to mount a longer focal length scope. My polar alignment is fine, any thoughts would be very welcome.

[Bizibilder]

Pulley loose?  Out of balance or Dec guiding switched off are my first thoughts.

[1parsec]

Hello Guy,

If you are getting drift in Dec and the guider isn't correcting then there are a couple of things to check.

(Even if the polar alignment is off the guider should correct the DEC error)

Check the DEC axis responsiveness.

You can see this by popping an eyepiece in the scope and setting the rate to x1.  When pressing North for a few seconds then South button, how long does it take for the DEC to show movement after changing the direction ?

Does this change when testing in the West when you had good guiding before and the NW now ?

If there is a long delay then there is excessive backlash in the Dec drive -

Is the mesh between the worm wheel set to a minimal amount ? Can you feel and 'slop' there ?

If the mesh is ok check the belt is tensioned correctly and the grub-screws holding the 12T and 47T pulleys are tight.

If the drive looks ok try a different guide scope with a fixed lens assembly.  The lenses in a camera lens may shift differently depending on the orientation of the lens. How is it mounted ?

Or put the guide camera in the main scope and check the guiding from there. If it's good in the main scope the issue is the lens internals or the ways it's mounted.

Thanks, Dave.

[Owmuchonomy]

Check the obvious. If it's like my HEQ5 you have to disconnect the cable connector for each axis to do the mod. Check the Dec connector hasn't come loose from the mother board. Also as above posts.

[Coco]

Update:  I have an overly tight DEC worm drive locking ring, strange that I was so tight, I cannot explain why. 

[sloz1664]

Hi Guy,

The reason your locking ring is tight is you may not have installed the spacing washers in their respective positions.

this is causing the binding of the DEC worm drive locking ring.

Steve