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CG-5 Declination Slew Speed

Celestron mount
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#1 HenryV1598

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Posted 11 July 2018 - 05:29 PM

I have an old Celestron CG-5 ASGT mount.  I hadn't used it in a while and brought it out and found that the declination won't slew at anything other than its highest speed.  Even when I try to do an alignment, normally it would use higher speed for the rough align, then go to slow speed for the fine align.  But even then, it's full speed.  I've tried doing a "quick align" and adjusting speed - but it stays at full speed still.  I've done a factory reset, but that changed nothing.  I've also swapped out hand controls for a newer one, still no good.  I have tried 3 different dec cables, and that's not the issue either.

 

So, at this point, I'm guessing it's in the electronics. From what I've gleaned from reading some other posts, the culprit could be the dec encoder, the dec board, or the main board.  Can anyone clue me in on how to check without replacing them all one-by-one?



#2 mclewis1

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Posted 12 July 2018 - 08:27 AM

There is no "main board" per se. The motor controller board handles both axis electronics. To check out the dec motor/encoder you can simply swap the RA and DEC connections to the motor controller board. You obviously won't be able to do an initial alignment but you will quickly see if the problem stays with the motor (which usually means it's the encoder on that assembly) or moves to the RA motor/axis (in which case the problem is most likely the motor controller board). In some cases a failure of the motor controller board isn't a component but instead a cold solder joint which if you can find the joint is relatively easy to repair.

 

While you are working the the cables internally it would good to carefully go over all the small connectors to see if you've got a bad pin or wire.

 

 

Edit: to clarify what you see when swapping the RA/DEC motor connections.


Edited by mclewis1, 12 July 2018 - 11:42 AM.


#3 HenryV1598

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Posted 12 July 2018 - 09:02 AM

Thanks, Mark, I'll take a look for cold solder joints.  Based on few other posts I've seen, I figured it was more likely to be a fried component. I've been planning to pull the whole thing apart, clean and re-lubricate everything anyway... so maybe I'll start on that this weekend.




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