I've owned an Orion SkyView Pro mount for almost 4 years, and a GoTo upgrade for almost 3. During a dust storm last week, my mount was outside (covered), and I found dust high on the mount legs. Soon after, both motors started exhibiting a groan when executing an extended full-speed slew. And the RA motor seized entirely (with a clackety sound) when slewing back to the home position.
I suspected dust in the gears was the culprit, so I removed the motors, removed the worm gears, removed the grease from all the gears (mount worm gears and shaft teeth included), and applied new bicycle bearing grease. The worm gears operate smoothly, and the motor gears operate freely.
The battery was 3 years old, so I replaced that, too.
To describe the groan, instead of a high-pitched whine, the motor pitch is lowered with a low vibration component. If I stop the slew and restart it, the motor reaches its full speed. And the DEC axis also exhibits the seizing behavior. And again, stopping and restarting the slew makes it proceed as normal.
In the months before the dust storm, the mount had started having drive-offs. While aligning a planet on my camera sensor, the motor would continue to slew after I released the movement button on the hand controller. Pushing the opposite button would stop it. I suspected my hand controller was having sticky control buttons, but these new behaviors seem to point to something different—like a bad motor control board.
EDIT: After writing this, I ran another test. New battery, fresh off the charger, 13.54V. The RA motor groaned right off the bat. Two tries, and it hummed along without issue. I let off the button once inadvertently, and again, another two tries to go without a groan. +360˚ and -360˚ rotations were smooth with no hangups. The DEC motor went through +360˚ and -360˚ rotations entirely without issue.
EDIT 2: I went through all the motor speeds. Ironically, speed 8 sounds like motor groan (each rate has a different motor tone). I also disassembled the hand controller. Other than a detached hot glue blob that escaped upon opening, everything was clean and all the button pads on the circuit board had minimal wear.
EDIT 3: I disassembled the motor control unit. In spite of its ventilation holes on the rear, it had no dust inside. So I'm suspecting the dust storm had nothing to do with the issue.
Edited by BQ Octantis, 26 September 2020 - 07:22 PM.