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Old 27-01-2013, 02:54 PM
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pvelez (Pete)
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Dodgy Robofocus motor?

I have a Robofocus that has ceased to play nicely.

It's attached to my Tak FSQ106. At times it ceases to move and the only way to get it running is to loosen the screws holding the motor to the mounting bracket. Sometimes this results in the motor running in the same direction irrespective of whether it is the in or out button that is pressed.

My suspicion is that the shaft of the motor is bent slightly.

Has anyone else had this experience?

Pete
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  #2  
Old 28-02-2013, 06:29 PM
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Logieberra (Logan)
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Pete, best email Jeremy at Technical Innovations for that sort of support. Good luck.
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Old 28-02-2013, 09:21 PM
rally
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Pete,

If loosening the screws works then it could be misalignment problem.
When you relax the mechanicals by undoing the screws it can align by itself and the friction ceases.

Maybe check that the bracket and the focus drive are at the right angle with respect to each other and make sure that the centre of the focus shaft aligns with the centre of motor output shaft

If you think the shaft is bent - remove it and let it rotate and see if it wobbles

As for the direction problem, does this happen when its been relaxed or when its in its "stressed" state !

Its possible that maybe there is a poor connection somewhere too - not sure how the steppers might behave if they are missing a phase or having excessive resistance on a phase either intermittently or permanently.

Rally
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Old 26-04-2013, 07:54 PM
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pvelez (Pete)
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Well, I thought I had sorted this.

I lugged the beast into Bintel and they played about with things for a while. It seems the RF is a tad touchy when there is a heavy load. I have a STL11k attached. So we (mostly Don) adjusted here, and tightened there and had it all humming.

I've had a few glorious nights out with the rig. Last night I managed about 6 hours of Ha of Eta Carinae and M8. Tonight - no joy. The focusser just hums and won't turn. I had left the scope on the mount under a Telegizomos cover which normally presents no issues. But tonight - no joy.

Some my current thought is that the humble RF is not quite aligned well enough and so the motor is not quite up to the task.

Any thoughts on this? Do I need a bigger motor? Or do I need to strip it all down and try to align it again?

More relevantly - has anyone else seen this issue?

Pete
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Old 26-04-2013, 10:11 PM
jase (Jason)
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Pete, misalignment could be the cause though I can't say I've experienced this myself. The STL11k and standard robofocus should be fine unless you've got an external filter wheel and other accessories.
Does it move in either direction at all?
Focuser draw tube lock is not down is it?
Have you tried recalibrating it to measure the focus in counts? Becareful here if you run FocusMax it you may need to redo v-curve runs.

The humming noise is natural when idle as its holding its position. If you are having camera 'holding' problems where the motor slips when it moves, increase the duty cycle percentage. 50% or 60% is normally enough.
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Old 27-04-2013, 08:34 AM
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pvelez (Pete)
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Thanks Jase

I agree it's probably misalignment. What troubles me is that it's so finicky. There are quite a few elements that can add to this including the shaft coupler and the focus shaft itself.

I took it off the mount last night. This am it runs fine.

Looks like its back to the work bench.

Pete
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