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Meade ETX 125 fork mount options

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#1 Ed Sunder

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Posted 03 November 2017 - 01:33 PM

I have a Meade ETX 125 that has great optics, but part of the central azimuth gear shaft is worn/broken - if I make sure to keep the telescope from travelling to that part of the shaft it's okay, but that's hard to do and if I screw up I have to open the thing up and do some work. I've tried to find some replacement parts, but that seems pretty difficult to do. I'm wondering if I can just buy a used ETX 90 or something smaller. Is the fork mount the same, just with different adapter parts (that I already have from my existing ETX 125)? Alternatively, does anyone have a ETX 125 fork mount for a reasonable price? If it needs a replacement altitude gear that works fine on mine and I could combine them. This is a great little scope that I use mostly for demonstrations and as a travel scope and I'd like to have it fully functional.

 

Any suggestions are welcome. Thanks!



#2 aneeg

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Posted 03 November 2017 - 02:37 PM

Defork it! And get a decent mount!

 

Arne



#3 carolinaskies

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Posted 03 November 2017 - 06:57 PM

I have a Meade ETX 125 that has great optics, but part of the central azimuth gear shaft is worn/broken - if I make sure to keep the telescope from travelling to that part of the shaft it's okay, but that's hard to do and if I screw up I have to open the thing up and do some work. I've tried to find some replacement parts, but that seems pretty difficult to do. I'm wondering if I can just buy a used ETX 90 or something smaller. Is the fork mount the same, just with different adapter parts (that I already have from my existing ETX 125)? Alternatively, does anyone have a ETX 125 fork mount for a reasonable price? If it needs a replacement altitude gear that works fine on mine and I could combine them. This is a great little scope that I use mostly for demonstrations and as a travel scope and I'd like to have it fully functional.

 

Any suggestions are welcome. Thanks!

You'll spend more time and money trying to fix this issue than most of us believe it's worth. 

However if you go over to Weasners ETX page http://www.weasner.c...x/techtips.html you'll see some information about these scopes.  You should be able to determine over there if there are any differences between your drive and smaller or different era ETXs.  

If you regularly use this telescope I would suggest upgrading to a better mount though.  It's easy enough to get a Vixen or Losmandy adapter for the scope and its so light that most any reasonably designed mount will work with it.  I'd go over to the mount forum here on CN and look at the reviews for some of the Alt-Az designs now available.   You might find you'll like even a dual mount system which would allow you to set up a second telescope on the same mount that has a different focal ratio adding to the ability to demonstrate the beauty of the skies! 


 



#4 EdIII

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Posted 07 November 2017 - 09:57 AM

I have a Meade ETX 125 that has great optics, but part of the central azimuth gear shaft is worn/broken - if I make sure to keep the telescope from travelling to that part of the shaft it's okay, but that's hard to do and if I screw up I have to open the thing up and do some work. I've tried to find some replacement parts, but that seems pretty difficult to do. I'm wondering if I can just buy a used ETX 90 or something smaller. Is the fork mount the same, just with different adapter parts (that I already have from my existing ETX 125)? Alternatively, does anyone have a ETX 125 fork mount for a reasonable price? If it needs a replacement altitude gear that works fine on mine and I could combine them. This is a great little scope that I use mostly for demonstrations and as a travel scope and I'd like to have it fully functional.

 

Any suggestions are welcome. Thanks!

Having never seen a diagram of parts for the ETX, I have problems understanding the terminology of the various components. If I am not mistaken, the azimuth function for this scope is in the base. Adding to my lack of understanding of your problem is how you could avoid using part of a gear or shaft while using a telescope. So, this seems almost too simple, but there is a right assention drive unit for this scope on EBay for less than $40. It has the motor and the gears. Is this a solution or do I just fail to understand the problem?

 

Ed



#5 Gargoyle

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Posted 07 November 2017 - 02:30 PM

De-fork. 



#6 Ed Sunder

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Posted 10 November 2017 - 01:49 PM

So the consensus is to de-fork it. I have an LX200 ACF that I could mount it on top of (I have the mounting hardware already) but that's not what I'm looking for since I really want to have something more portable (which my LX200 is not). My biggest hesitation is that I have the case for the scope and having the case makes it so much easier to move around that I love the idea of just either fixing or replacing the existing structure so that I can keep using the case. I also already have a Meade field tripod (this guy: https://www.astronom...ipod_p3588.aspx) so that's why I'm leaning toward fixing. Maybe I should just sell the case and the tripod and get a completely new base/tripod.

 

Thanks for the advice, folks.


Edited by Ed Sunder, 10 November 2017 - 01:50 PM.


#7 EdIII

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Posted 18 November 2017 - 07:18 AM

Looks like this thread has run its course, but it raises unanswered questions. I did a search, but have not been able to get get further information. Question: what is the nature of the problem here that causes everyone to agree that this scope is not worth repairing from a cost or time standpoint?

 

I had a friend call me with what sounds like could possibly be an identical problem. He is bringing his ETX 125 over tomorrow and we are going to look at it together. Symptom, clicking in base during GOTO operation and maybe tracking, that point was not clear to me. He sent it to Meade a few months ago. He says they returned it with a note that they could not repair it.........charged him anyway plus shipping both ways and he says shabbily reassembled it. He is not a happy camper. Anyway, it seems he has nothing to lose, so we plan to see what we can find.

 

Again,  what is the nature of the problem with the azimuth mechanism that is causing everyone to agree it is just not worth repairing, even Meade ? We are both retired, so the time is free and we both like challenges !!

 

Ed



#8 sickfish

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Posted 18 November 2017 - 07:49 AM

Defork it buy some rings and vixen dovetail then get an alt az mount.

Maybe Twilight 1



#9 *skyguy*

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Posted 18 November 2017 - 09:25 AM

Contact Meade and see if they will take your broken scope and replace it with a new one at a substantial discount. The do have a generous trade-in program that they don't advertise, however I don't know if it is available for all their telescopes.

 

If you're only interested in repairing your scope, contact Don Rothman at Astro Parts Outlet.  He's been able to supply me with some very hard-to-find telescope/mount parts at a very fair price. Call or email him, don't rely on his online parts list.

 

http://astronomy-mal...o.parts.outlet/

 

Good Luck getting your scope fixed ...


Edited by *skyguy*, 18 November 2017 - 09:26 AM.


#10 EdIII

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Posted 18 November 2017 - 10:24 AM

Thanks, this will be repair or part out as I understand it.

 

From another issue on another scope, trade in is not an option. Getting off the subject now, but the Meade offer is trade in for $450 plus shipping. That’s $500 plus $50 to send them the old unit.....total $550. You can buy a new ETX125, shipped for $650 for a difference of $100. Would you take $100 for a complete but disabled ETX125? I wouldn’t. I would be glad to pay that !!!

 

So the question remains as to what it is about this scope that makes everyone say, defork. I guess we will learn tomorrow when disassembly starts.   

 

Ed



#11 John Rose

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Posted 18 November 2017 - 08:53 PM

Why so many comments to defork instead of repair?  My experience is the optics are better then the mechanics.  Also which version is it?  The latter ones are a bit better.  There was a change in the fork arms and the old tubes do not fit on the latter mounts.  When disassembling be careful and very patient.  Some of the screws are glued in and horrible to get out.  I know.  I repaired an ETX105 by removing the RA motor from a 125 base.  Seemed simple enough when I started!

 

John  



#12 EdIII

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Posted 18 November 2017 - 09:52 PM

Hope I have not hijacked this thread. We are still on the same subject. OP has stated he prefers to repair rather than defork and gave his reasons. So would I, in spite of difficulties. Admittedly, I do not know what I am getting into. Nothing to lose, so it does not matter. We will be tackling the 125 tomorrow and I have another in my workshop that I purchased strictly to use as a learning scope on the mechanics.

 

My primary scope is a 125 also. It is my first GOTO, so I don’t yet know what is available that is better. I have been using it about 6 years. I do know that when I train the drives, calibrate the motors, level the scope, point it North then align it, it finds things. I sync on a star nearby and the object I want is nearly always in the field of my 32 mm. Until I learn better, to me, that is fantastic !! 

 

Glued in screws, that doesn’t sound good ??? Anyone else have anymore info on going into the azimuth section? Need all the help I can get !!!  smile.gif

 

Ed 


Edited by EdIII, 18 November 2017 - 09:54 PM.


#13 nitegeezer

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Posted 19 November 2017 - 12:42 AM

Just take pictures very regularly as you take it apart.  They could help you assembling and may help someone else down the road.

 

Good Luck and keep us posted!



#14 EdIII

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Posted 19 November 2017 - 01:00 PM

My buddy called in sick. I am disappointed that we will not be disassembling his ETX125 scope today. Hopefully, he will bring it over soon. Yes, I will take pictures and post some of them whether it is a success or failure.

 

Ed



#15 E Sully

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Posted 19 November 2017 - 03:43 PM

The clicking could be a crack in the motor drive board mount, or damaged worm gear causing the gears to skip.

I don't know of glued in screws being an issue.  I have opened up my ETX90 with no real problem.  There is currently an RA motor board available 39.95 at Telescope Warehouse http://shop.telescop...c?productId=590, and for 49.95 on Ebay.   This is an assembly that consists of a mounting board, motor, and gear set.

Trying to disassemble the complete scope is very difficult, but it is not that hard to remove and replace the board if that is the issue.

The scopes work well, but cannot handle a lot of stress or extra weight on the drives.

My ETX90EC is about 15 years old and still running well.  I did have an issue with a wire in the base creating a motor fault, but a little solder and heat shrink fixed that.



#16 EdIII

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Posted 04 December 2017 - 09:09 PM

I guess my buddy has other compelling interests right now. I have not heard from him. I did have an opportunity to go into an ETX125 today and I took advantage of it. What I learned may be what is already known, but here it is FWIW.  I removed everything from the right fork arm, put it back and adjusted it. 

 

I went into the base and continued until I needed a spanner wrench, I believe. I had to quit there, so I reassembled and adjusted the gears. Both assemblies worked perfectly. I believe I pulled the gear the OP was talking about. It meshes with the ra worm. I will add a photo after I post if possible. I have to go out of the forum and resize it. The gear appears to be attached to 1/2 of the ra clutch mechanism. As mentioned earlier, the motor, plastic gears and worm are available at a reasonable cost and not difficult to replace if someone has mechanical tools and abilities. The metal gear that is attached to the clutch is also not a difficult job, but not sure where you would find it and perhaps that is the difficult job here.

 

Ed

 

The first photo shows the ra clutch mechanism. The metal ra gear is on the back of the half that is still attached.

09AB9C34-05A4-474A-9A4C-1E3145A461F7.jpeg

 

The second photo shows the back side of the clutch and the ra metal gear. 

947A6021-3D69-4FA4-AA0D-BFC64880910F.jpeg

 


Edited by EdIII, 04 December 2017 - 09:29 PM.


#17 EdIII

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Posted 04 December 2017 - 09:40 PM

After this shot, I removed the motor and worm before running into the roadblock. The roadblock was needing a spanner wrench to remove the large nut seen in the center of the scope. I may try it again one day if I can find or make the spanner wrench. Removing that would allow the main two bottom pieces to separate, I believe.

 

Ed

 

 

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#18 E Sully

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Posted 05 December 2017 - 11:31 AM

You can buy a brake line wrench for that nut.  They are slotted so it can be used with the wiring in place.


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#19 EdIII

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Posted 05 December 2017 - 07:12 PM

I will see if I can locate that wrench. 

 

It it has been mentioned several times that all ETX scopes are not created equal !! It appears to me the ones with plastic forks and bases may have confused people and given all of the ETX scopes a bad name. I have two scopes and an additional mount plus some additional spare parts. All of mine have the metal right fork and base. I hope to be able to keep my scopes going for a long time.

 

I had read that the RA central bearing on these scopes is plastic or nylon. Again, I don’t think that is true of all of these. The one I am working on now appears to have needle bearings under that large nut. It really moves easy and smooth.

 

Ed



#20 OzAndrewJ

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Posted 05 December 2017 - 09:45 PM

Gday Ed

 

Have a squizz at

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

Yours looks like a std PE version so should be similar.

How smoothly it moves depends very heavily on that preload nut.

I had hours of fun trying to figure out what was happening with the 6 mounts i worked on.

As to needle bearings, you will see a ref to "SKF AXK3552" in my writeup.

I couldnt try fitting them as the units i was working on were "new" items

inside the vendors workshop, so had to be kept standard,

but 2 people have reported doing that mod with no problems.

Just spend time getting the worm preload correct so it spins without too much torque

but reduces the endplay, as that reduces the stress on the arm that links the

gearbox to the worm gear.

Having the needle bearing in there makes that much simpler

as there is virtually no torque required to move the base.

 

Andrew Johansen Melbourne Australia


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#21 EdIII

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Posted 07 December 2017 - 09:27 AM

Thanks. Been reading your article. Very good. A couple of questions.

 

First, I was having trouble getting the ra assembly apart while protecting the wires that run through the middle of the bolt. Nothing broke, but actually I am surprised it didn’t. How did you get the clutch apart while protecting the wires?

 

Second question. Your article recommends replacing the central shaft bolt with a threaded rod. It appears to me the bolt is hollow and the wires go through it. How would that work?

 

Did you make a spanner wrench to remove that big round nut that holds the two bottom assemblies together?

 

Perhaps I need to disassemble a little more to see those areas. I am going to do this again after I have time to absorb what you have written. It is reallly helpful.

 

Thanks,

 

Ed



#22 OzAndrewJ

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Posted 07 December 2017 - 02:38 PM

Gday Ed

 

How did you get the clutch apart while protecting the wires?

I actually removed the OTA and one fork arm.

That allowed me to lift the plastic cover over the top of the base enough to loop the wires over the top of the bolt as i rotated it, thus avoiding it wrapping/cutting as i undid the bolt.

I knew from other ( damaged ) mounts how it went together, and that where the wires came out at the top, the edges of the hole were like a razor blade, so didnt risk forcing it and cutting/shorting any wires.

 

 

Second question. Your article recommends replacing the central shaft bolt with a threaded rod. It appears to me the bolt is hollow and the wires go through it. How would that work?

As you learnt, the current design is a total PITA to get apart, as you need to release the bolt enough to free up the dog clutch joint between the alloy casting and the lower clutch plate, before you can unscrew the lower clutch plate.

My thought was to use a hollow threaded rod identical to the the current bolt, but with a threaded top ( vs a hex head ) and the slot cut all the way to the top.

Now you loctite the threaded joint at the clutch end and place a nut on top to do the tensioning.

Turning the nut still tensions the clutch as per usual, but if you ever need to disassemble it, you just release the nut.

By leaving enough free wire inside the base side to pull it fully back out, you can always remove it as per now to get at anything you want, and the slot allows the bolt to pull down without snagging on the wires at the top.

 

 

Did you make a spanner wrench to remove that big round nut

Nope, i borrowed a wrench from the vendors as they already had a unit.

It was a short length of thick walled pipe with pins set into the end face, so it could be used like a TBar.

 

Andrew Johansen Melbourne Australia


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#23 EdIII

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Posted 07 December 2017 - 03:49 PM

Ahhhhsoooo. Thank you.  Next project is making the spanner wrench. Fortunately everything is working, so no hurry........just a learning experience.

 

I rebuilt SCUBA regulators in another life. Had to make numerous spanners for different regulator bodies. I wouldn’t be surprised to find a suitable wrench in some of that stuff........if I can remember where I put it !!   lol.gif

 

Ed




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