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Brian Risley
Carpal Tunnel
*****

Reged: 09/04/06

Loc: SW Florida
ETX 125 Alt Clutch/Stops - Metal Fork Arm
      #5749023 - 03/22/13 03:42 AM

I am having some issues with an ETX-125 and the Alt controls. This is the metal fork version, as I have seen major differences in the 'fixes' posts here and on Weasner's site showing the plastic arm versions and notes about the metal version taking care of a lot of the problems seen in the plastic versions.

I want to make sure the the parts for the clutch are all present. I have the plastic knob, with a 1.25" metal plate at the base of the screw. This goes against the setting circle ring (the one with no #'s). Next is about a 1/2" across by 1/8" ring that appears to be the clutch. This goes against a piece of metal inside the bearing assembly that is connected to the gear that the worm drives. (What is odd is we see a wear point on the OUTSIDE of the setting circle plate about the same size as the ring! I don't remember there being a washer there, so that is one reason I am asking for specifics about that area.

Now what my problem is, if I loosen the knob, the scope moves freely, but the assembly behind the bearing that has the hard stops appears to be interfaced to the gear that the worm turns. In other words, if I have it turned full up against the stop, loosen the knob and put the scope horizontal, I am still against the stop if I attempt to drive it further up. I would think that the stop would be tied somehow to the tube cradle position, not the gear assembly. (The manual makes no comment about having to pay attention to the position, it says to turn the knob to release and manually move it, so I think that it normally is in sync with the cradle.
I have not found any good take apart diagrams for the metal fork systems, including getting to the hard stop area.
How loose should the worm assembly be when it is removed. Should it spin real free, or is there some resistance expected? (It appears to have some rubber parts in it, not all metal faces.)
What should one look for in adjusting the worm? They have one screw that you can't get to once the cover is replaced and from my experience, you have to at least have the worm assembly loose to get it connected to the motor assembly, so trying to adjust it before inserting the motor (ie manual feel on the shaft play) is not possible.

This unit has given me fits. Any help in getting it to operate properly would be greatly appreciated.
I replaced the motor with one from George as the prior one had fried and I wonder if this resistance I feel is part of the problem that took it out in the first place.

Another example, move it to the lower stop area, it changes pitch, but still will drive on, but the knob will not turn with the scope, it starts to loosen the knob up!
It would be nice if Meade would document the assembly and how it operated.
Brian


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: Brian Risley]
      #5749030 - 03/22/13 03:59 AM Attachment (53 downloads)

Gday Brian
Quote:

Next is about a 1/2" across by 1/8" ring that appears to be the clutch




Thats not the clutch
That ring sits proud of the end of the axle.
When you tighten the knob, the ring pushes against the outside of the inner bearing race for the small bearing. The inside face of the bearing race then presses against the "outer" clutch plate ( which fits to the axle using a slotted keyway ), thus clamping the clutch plates to the worm wheel.

The inner clutch face is a washer that is locked to the plastic housing.
Have attached a side view of the exposed mechanism.

Andrew Johansen Melbourne Australia


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5749031 - 03/22/13 04:06 AM Attachment (54 downloads)

And heres the end view

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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5749035 - 03/22/13 04:09 AM Attachment (42 downloads)

and heres the little washer that provides the preload via the bearing race

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Brian Risley
Carpal Tunnel
*****

Reged: 09/04/06

Loc: SW Florida
Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5749286 - 03/22/13 09:36 AM

Ok, I got the black plastic assembly out, but all the other parts are still in the arm. The inner large bearing is not coming free. Is there a simple way for someone without a machine shop to get that bearing out. I think the key was not making a locking contact, it came out still in the groove on the plastic shaft and really had no bite that I could see. (Or is the solution to pull the smaller front bearing, line things up then put the key in to the assembly from the front?
Thanks for the help.
Brian


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: Brian Risley]
      #5750166 - 03/22/13 04:53 PM Attachment (35 downloads)

Gday Brian

Quote:

Ok, I got the black plastic assembly out, but all the other parts are still in the arm.




You will probably need to get them out, even if only to clean the clutch faces.
Quote:



The inner large bearing is not coming free. Is there a simple way for someone without a machine shop to get that bearing out.




Once the guts is removed, you should be able to push out the outer bearing. Once that is out, the hole will be large enough for you to poke a wooden stick through, that can be used with a smal hammer, to tap out the large bearing. When you tap, just work gently in a circular fashion to slowly get the bearing walking out without binding. Only tap against the outer race when doing this. It should move relatively easily.
Mine just slid out, as per the piccies.
Have attached a shot of what it looks like inside through the large bearing hole, and how much outer bearing race you should be able to see to tap against.

Andrew Johansen Melbourne Australia


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Brian Risley
Carpal Tunnel
*****

Reged: 09/04/06

Loc: SW Florida
Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5750186 - 03/22/13 05:05 PM

Andrew, Problem I have is that the inner bearing is not budging too. All the parts are stuck inside between the bearings.
I have some Kroil, should I apply a few drops around the outside of the large bearing to see if that will free it up?
These pictures are great! Should help others in understanding how this all works!

Brian


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: Brian Risley]
      #5750249 - 03/22/13 05:31 PM

Gday Brian
Quote:

All the parts are stuck inside between the bearings.




Then remove the worm ( it is seperate from the gearbox )
and gently pry/push the wormwheel itself out sideways.
Once that is out, the rest will follow,
and you can get access to the inside faces of the bearings.
In my unit, the small outer bearing was a sliding fit,
which is required for the clutch to work properly.
I actually used some very fine wetndry paper ( about 1200 grit )
to clean out the bearing faces, and when i reassembled it,
i used a light machine oil, just to ensure it didnt bind up.

Andrew Johansen Melbourne Australia


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Brian Risley
Carpal Tunnel
*****

Reged: 09/04/06

Loc: SW Florida
Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5757342 - 03/26/13 01:09 AM

Andrew, Thanks for the info.
It appears that the clutch plate had the key break off. I thought the key was a separate part inserted but your picture shows it as part of the main metal assembly.
Geo. has one so hopefully that will get us back up properly. I had gotten it to hold, but after doing a bunch of gotos, the clutch slipped and shifted the stops.
(My gear would not come out through the side, only the clutch and the back lock washer.)
Brian


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: Brian Risley]
      #5757522 - 03/26/13 05:34 AM

Gday Brian
Quote:

It appears that the clutch plate had the key break off.




I must admit i find that hard to believe ( if it is like mine )
In mine, the key on the floating clutch plate had actually mangled the slotted plastic keyway, vs break.
The floating clutch would have to be hit with a sledge hammer to damage it ?????

Andrew Johansen Melbourne Australia


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Brian Risley
Carpal Tunnel
*****

Reged: 09/04/06

Loc: SW Florida
Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5776831 - 04/04/13 12:03 AM Attachment (21 downloads)

Well Andrew, it was definitely broken off. Got a replacement from Geo. (This scope belongs on the twilight zone!) Alt tested fine after replacing this (after replacing the Alt motor assembly (after replacing the alt motor board, which Geo tried to repair (just to see if he could) and let the flame out of a chip!)). Put it all back together, then went to put it through its paces. Guess what, the AZ shorted out somehow!
Upon investigation it appears that the black motor lead on the back of the AZ motor may have made contact with a screw head located real close to it. Geo. sent me an AZ drive board. It now appears to be working properly! (Thanks George!)
This scope was known for some odd issues and sporadic weirdness such as phantom gotos etc. I am leery that the problem may have been intermittent contact with the screwhead. (I pushed it away with a very small flat blade, so it shouldn't be a problem anymore.)
If anyone else experiences odd behavior, check this out, real easy to do as you just have to remove the 3 base screws to look at the back of the AZ motor and see that you see daylight between the tabs on the back of the motor and screw located there.

Brian


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: Brian Risley]
      #5777887 - 04/04/13 02:51 PM Attachment (20 downloads)

Gday Brian
Quote:

Well Andrew, it was definitely broken off.




Got any piccies of it???
In my unit, the DEC axle could move approx 25-30deg in DEC
even when the clutch was tight.
The reason was the clutch plate key had actually chewed into the plastic of the axle, thus shearing sideways through the plastic keyway, vs break the clutch plate.
I cant even imagine how the clutch plate would break.

Andrew Johansen Melbourne Australia


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Brian Risley
Carpal Tunnel
*****

Reged: 09/04/06

Loc: SW Florida
Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5778770 - 04/04/13 11:12 PM

I learned some more about this scope when I returned it to its owner. It had taken a fall against a concrete wall edge. There is a dent in the OTA. I suspect this caused the problem with it. (Optics are still aligned well, I did some tests with it earlier and star tests looked great.)
We'll see how it works out for him.
Brian


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tomatohead
member


Reged: 11/21/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: Brian Risley]
      #5779722 - 04/05/13 02:18 PM

I've been lookin all over for information on the dissassembly of the right fork arm. My 125 is identical to the one in the pictures but I still am lost on how to do this. Mabe someone with good drawing skills could come up with an "exploded" view of the right fork/clutch assembly and detailed instructions

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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: tomatohead]
      #5779831 - 04/05/13 03:03 PM Attachment (40 downloads)

Gday TomatoHead

Basically,
remove the OTA,
remove the outer plastic cover on the fork arm,
loosen/remove the DEC worm assy
push out the axle

You may need a jig to push out the axle, depending on how tightly it is fitted, but there are several ways to do that.
I have attached a diag i made when i took mine apart.
I cant guarantee later ones are absolutely identical, but the basic assy mechanism will be the same.

Andrew Johansen Melbourne Australia

edit ( my uploaded zip was corrupted )


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tomatohead
member


Reged: 11/21/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5781636 - 04/06/13 11:45 AM

Thanks OzAndrewJ that was exactly what I was looking for!
Just a couple of questions though;
Do I have to remove the base bottom cover to access screws to remove the right arm plastic cover? And will the right tube adapter have to be removed to access the clutch faces?

Thanks again


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OzAndrewJ
scholastic sledgehammer
*****

Reged: 11/30/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: tomatohead]
      #5782296 - 04/06/13 05:54 PM

Gday TomatoHead

Quote:

Do I have to remove the base bottom cover to access screws to remove the right arm plastic cover?




I didnt on mine. Just undo the 5 internal screws and the outer cover just falls off.

Quote:

And will the right tube adapter have to be removed to access the clutch faces?




Yep, if you want to do anything meaningfull.
In mine, as per the earlier photo, the keyway was damaged and hence the outer clutch face was able to rotate in the keyway.
This happened because my inner "fixed" clutchface was slightly bowed ( convex ), and hence wasnt gripping properly / at all.
I was planning to machine it out to take a fibre washer, but after i had fixed the keyway, it held well enough, so i left it.

Andrew Johansen Melbourne Australia


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tomatohead
member


Reged: 11/21/10

Re: ETX 125 Alt Clutch/Stops - Metal Fork Arm new [Re: OzAndrewJ]
      #5782697 - 04/06/13 09:51 PM

Thank you VERY much.

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