Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Uh oh. Worm gear drive seems to have stopped.

  • Please log in to reply
7 replies to this topic

#1 Borodog

Borodog

    Apollo

  • -----
  • topic starter
  • Posts: 1,307
  • Joined: 26 Oct 2020

Posted 20 February 2021 - 12:13 AM

On my ~1985 Celestron-Byers Worm Gear Drive C8. The light is still lit but there is no sound from the drive unit and she does not track. What should I look for as likely sources of the problem?

 

 



#2 Benschop

Benschop

    Vostok 1

  • *****
  • Posts: 151
  • Joined: 12 Jan 2015
  • Loc: Eastern Ontario

Posted 20 February 2021 - 02:11 AM

You will need to first, with power unplugged, use an ohm-meter to measure across the AC terminals at the scope, to determine if the motor is in circuit. If it measures open circuit, trace to the motor. If still open, then you will need to replace the motor. If you have resistance on the meter, then the winding is in circuit. Then you will need to separate the synchronous AC motor from the small gearbox under the motor. Once separated, check if the motor is turning while plugged in. If the motor is turning, it is quite possible that the small gear on the motor shaft is slipping on the shaft. If that is the case, it is an easy fix. However, if the gear is tight on the motor shaft, and the motor is turning but the worm gear is not, then you will need a gearbox.

 

If the AC motor is not turning, or if the winding is open, or if the gearbox is bad, there are people here on CN (eg George) who might have spare parts  - I can pass their contact info to you.

In any event, it is not a complex nor expensive repair, once you locate the source of the issue and a replacement motor/gearbox.


  • Littlegreenman and Borodog like this

#3 Benschop

Benschop

    Vostok 1

  • *****
  • Posts: 151
  • Joined: 12 Jan 2015
  • Loc: Eastern Ontario

Posted 20 February 2021 - 02:26 AM

Have a look at this album...

https://www.cloudyni...ve-disassembly/


  • Borodog likes this

#4 Borodog

Borodog

    Apollo

  • -----
  • topic starter
  • Posts: 1,307
  • Joined: 26 Oct 2020

Posted 20 February 2021 - 08:05 AM

Thank you both. I will dig into this today and report back my findings.

#5 Borodog

Borodog

    Apollo

  • -----
  • topic starter
  • Posts: 1,307
  • Joined: 26 Oct 2020

Posted 20 February 2021 - 09:28 AM

Update. I took the cover plate off of the drive unit. I plugged the unit in and listened carefully, and lo, I could hear the motor turning. I shot a time lapse and the worm gear was also turning. I believe the forks were locked at the time, but I may be wrong, as I locked and unlocked it a few times to rotate the forks. In any event, I set up to shoot another time lapse to see if the OTA and forks were now rotating. They were not, and lo, now the motor and worm gear have stopped, locked or not. The motor was warm to the touch; I am not sure if that is unusual. I have unplugged it to let it cool and will test again when it has cooled down.

Edited by Borodog, 20 February 2021 - 09:29 AM.

  • Benschop likes this

#6 Borodog

Borodog

    Apollo

  • -----
  • topic starter
  • Posts: 1,307
  • Joined: 26 Oct 2020

Posted 20 February 2021 - 09:39 AM

I think this must mean the big gear is intermittently binding, yes? Perhaps it needs to be lubricated? For what it’s worth the inside of the base is very clean; the motor looks original but in such good condition it could be new, and the worm gear is well lubricated with shiny oil; no gunk accumulated.

#7 Benschop

Benschop

    Vostok 1

  • *****
  • Posts: 151
  • Joined: 12 Jan 2015
  • Loc: Eastern Ontario

Posted 20 February 2021 - 01:46 PM

Great that it is turning. I do not know how warm these old motors get. Perhaps possible that the gearcase internal grease is getting old and gummed up?



#8 Borodog

Borodog

    Apollo

  • -----
  • topic starter
  • Posts: 1,307
  • Joined: 26 Oct 2020

Posted 20 February 2021 - 07:57 PM

It's 100% the small gearbox attached to the motor, which I believe come as a unit. It looks like the thread posted by Benschop is on the money; amazingly, that guy's scope is also a white tube C8. I believe it had to have come from the same batch of 100 that mine did, as they are the only white tube Celestron-Byers WGD C8s that I know of in existence.

 

I tried to remove the worm gear coupler from the drive shaft, but apparently the allen head screw is ever so slightly larger than 1/16". I didn't want to keep at it for fear of stripping out the allen well in the screw head. I suppose it must be a 1.6mm allen wrench or something?

 

Frankly, I am not the handiest person in the word and I am not looking forward to trying to build my own coupler to couple to the coupler, as had to be done in the linked thread because the shaft on the new motor is the wrong size. Is there anyone on here that would be willing to replace the motor for me on a commission basis? I can ship the base; the whole unit does not need to go. Please PM me if you can or know someone who can.


Edited by Borodog, 20 February 2021 - 07:58 PM.

  • Benschop likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics