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

ETX125 Not rotating around azimuth

Meade
  • Please log in to reply
8 replies to this topic

#1 stucker23

stucker23

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 01 Apr 2021

Posted 03 April 2021 - 09:04 PM

I have a Meade EXT125 telescope which I had not used for many years and on using it recently with Autostar I found that whilst the motor drive was working the telescope
does not rotate around the Azimuth when using the Autostar. I have taken the bottom off the scope and all appears to be working.
I turn on the Autostar and when getting to the Easy alignment option, I press the left or right, the motor starts, all the cogs turn, including the worm drive and
including the cog around the shaft, so all is working as it should there. Also the tension lever is working as when I turn it, I get the usual pressure and can also
see the end of the shaft, where the wires come out, also turning. Also the large black disc is slightly loose when there is no tension but when I tighten the tension
lever, there is no movement at all in the black disk so that also appears to be tightening in conjunction with the torque lever tension being applied.
 
So everything seems to be working other than the telescope itself is not rotating.
I have read that it may be associated with a lubricant issue or the clutch is slipping maybe because it was unused for a long time? I have read all the articles here
about pulling the shaft out etc which all seem horrendous so hoping that someone might know the simple answer and fix.

I can add that when I took the bottom off I noticed that the plastic bracket that goes around the larger white cog connected to the worm shaft was cracked and that
the screws holding that part were loose which may be why that cracked, however I have removed that cracked portion and tightened the screws and all the cogs engage properly.
This is not the cause of the problem as mentioned above, all cogs engage and turn, it's just the shaft itself that presumably turns the scope is not engaging or slipping.


Picture attached. Hoping someone has a solution.

Attached Thumbnails

  • Scope.jpg

Edited by stucker23, 03 April 2021 - 09:08 PM.

  • Widge likes this

#2 OzAndrewJ

OzAndrewJ

    Fly Me to the Moon

  • *****
  • Posts: 5,237
  • Joined: 30 Nov 2010

Posted 03 April 2021 - 09:36 PM

Gday Stucker23

Strange symptoms, but it might be a slipping clutch

When you back off the RA clutch knob, can you manually rotate the azimuth axis through about 700degrees???

 

Andrew Johansen Melbourne Australia



#3 stucker23

stucker23

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 01 Apr 2021

Posted 03 April 2021 - 10:49 PM

Hi Andrew, thanks for your reply. Interestingly, I seem to only be able to rotate it about 320 degrees, certainly less than 1 full turn. Is this an indication of the issue?

#4 OzAndrewJ

OzAndrewJ

    Fly Me to the Moon

  • *****
  • Posts: 5,237
  • Joined: 30 Nov 2010

Posted 03 April 2021 - 11:20 PM

Gday stucker23

If that is the case, then it sounds like something has gone wrong with the hardstop mechanism

and that will require a full base disassy. ( This is not trivial, as releasing the clutch is a pain )

Ref http://www.weasner.c...f_ETX125PE.html

 

Pic5 shows the main axial thrust bearing ( white inner disk )

and the hardstop washer ( greenish disk with tabs at each end ) spins around it.

You can also see a small pin at about 2 o'clock

Pic6 shows the upper section and you can see ( very faintly )

another small pin at about 8 o'clock

 

When you rotate the forks, the pins are at different radii so can go past each other.

Rotating one way, one pin connects to the tab on the washer and the whole washer then rotates

until it stops on the other pin.

When you spin the other way, the washer stop moves freely away from the base pin

until the other side of the washer connects with the base pin.

This then movves the washer away from the upper pin  ie  spins about 320deg till it hits the pin on the other side

thus giving near 700deg of motion.

If you only get 320 deg, then something is stuck somewhere

( one thing i have seen ( ie extremely rare ) was the outer pin got jammed in the tab slots

thus reducing movement, but as noted, that is extremely rare.

How much force did you apply???, ie maybe the washer is just stuck a bit

If so, try a little more pressure to see if it breaks free, but dont use excessive force.

You need to do this on both ends of travel, as if it is stuck, you wont know which way breaks it free.

If you still cant get more than 320deg then you need to dig a bit more.

 

Andrew Johansen Melbourne Australia


  • osbourne one-nil, M57Guy and Widge like this

#5 stucker23

stucker23

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 01 Apr 2021

Posted 03 April 2021 - 11:33 PM

Hi Andrew thanks again for further information, certainly lots to read through and try which I will hope to get to this afternoon. In relation to how hard did I try
to rotate past the stops, it does seem to come to a reasonably solid stop when rotating either way and I've tried a little extra force, as much as I am game to
and wasn't able to get any more so seems that the stops each way are solid. I'll work through your notes and update with any outcomes.

#6 stucker23

stucker23

    Lift Off

  • -----
  • topic starter
  • Posts: 4
  • Joined: 01 Apr 2021

Posted 14 April 2021 - 04:20 AM

An update on this problem is that as I was reluctant to disassemble anything, I simply took off the torque lever and rotated the lever slightly and then
reconnected it, just in case the torque lever was stopping at a point prior to there being full tension, although I was reasonably convinced that prior
to this that it was fully torqued. I then tightened the tension again and to my relief, the scope then started to rotate around the Azimuth,
so possibly it just wasn't fully tensioning.

#7 OzAndrewJ

OzAndrewJ

    Fly Me to the Moon

  • *****
  • Posts: 5,237
  • Joined: 30 Nov 2010

Posted 14 April 2021 - 04:36 AM

Gday Stucker23

Good to hear the clutch is now gripping, but that doesnt explain the fact

you dont have 680 deg of travel in RA when declutched.

Sooo, if you declutch, how much can you rotate the RA manually????

 

Andrew Johansen Melbourne Australia



#8 Widge

Widge

    Lift Off

  • -----
  • Posts: 12
  • Joined: 20 Aug 2020

Posted 24 July 2021 - 01:37 PM

Hi

Sorry I emailed you directly before I realised it was you who wrote this reply.

I am a newbie to
astronomy and last year I picked up a meade ETX125 cheap as it had
various faults one of which was a broken gearbox similar to the
article you wrote in Weasner's Meade ETX Tech Tips,
http://www.weasner.c...f_ETX125PE.html

I fixed the broken gearbox and thought I was on my way but broke the
gearbox again as it appeared to try and go past the endstop.

I have since realised the the scope will only rotate about 300 degrees
so there must be a problem with the endstop mechanism, I can see what
I need to get to (displayed in pic 5 of your article) but I am unable
to remove the aluminium baseplate.
I am presuming the the aluminium ring with the 2 holes in is a big nut
that needs to be undone, I have tried things like long nosed pliers to
undo it but it wont move, but before I take the next step and
fabricate a tool, I wanted to check that this was how it comes apart
and that I was not doing something stupid.

Any tips or advice welcome

Regards

Dave Widgery
Herault
France

#9 Widge

Widge

    Lift Off

  • -----
  • Posts: 12
  • Joined: 20 Aug 2020

Posted 30 July 2021 - 02:33 PM

I after dismantling the cluch and separating the base I found out what was stopping the scope rotating no more than 300 degrees, it was the gearbox mounting screw nearest the center of the scope, the plasic loop on the gearbox had broken allowing the screw to act as an additional pin stopping the endstop washer from rotating more than 300 degrees.


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





Also tagged with one or more of these keywords: Meade



Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics