I've recently bought a used AP900 and just ran the backlash tests in
Ray's Pulseguide app.
I found a load of Dec backlash - so much that the tests didn't reverse
direction at all.
I needed a backlash setting of 87 in the driver to correct for the
Today I went to follow the instructions on the AP website to adjust
the Dec worm adjustment (using the advice of finger pressure rather
than a hammer!).
The first thing I noticed was that the grub screw locking the hex bolt
in place was still present, so presumably the adjustment had never
been done before since the instructions say to remove and discard this
However, although I could loosen the grub screw, I couldn't remove it
completely - it unscrewed to the point of contacting the Dec motor
housing but I couldn't get it out completely. Is there a trick to
Secondly, once I had loosened the bolt and retightened with finger
pressure pushing on the motor housing, the instructions said to remove
the shaft cover and ensure the shaft could be rotated by hand without
binding. However, I couldn't remove the shaft cover.
Does it screw on, or is it a push fit? Any tips for removing it