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Overseas & Need Help on C8 RA Lock

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#1 rolandlinda3

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Posted 26 January 2013 - 11:02 PM

Hi observers. My wife and I are at the school where we sent our classic C8 (9V powered,short tripod with wedge, fork armed C8 OTA). We returned in part to retrain its use and found some little issues. Corrected a couple, but one I need some help on: the RA lock, when you tighten it down, is not locking the arm rotation well enough, and the little arm that used to pass over the slow motion knob is now hitting it. The clock drive works fine, so the gears are OK, but I don't know how to correct the RA lock so it holds better (more resistance). I fear going inside unless I know what to do, and the manual says nothing. I have operate 8s quite often but have never had the issue. What do I do? You can give me a link (if its not graphics heavy...we have limited connection) or give instructions. Thanks for reading.

#2 Brian Risley

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Posted 26 January 2013 - 11:44 PM

Roland, the RA lock lever should have a setscrew on it. You can release the screw and remove the lever. You should then see that the shaft has a slot in it for a screwdriver. Turn it so that the it just barely locks the motion. Then place the lever back on it about midway position and tighten the screw. You should then be able to release it and have free motion and tighten it and have it lock firmly. Halfway should be able to keep it from slipping but still be able to make adjustments with the RA slow motion knob. If you don't get it quite right, a few attempts at setting it should give you what you want.
If it won't tighten down, then possibly the lock plate on the inside has come loose. This will require going into the mount, but that is not too bad to do.
Let me know how it goes,
Brian

#3 rolandlinda3

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Posted 27 January 2013 - 08:56 PM

Brian, thank you very much for your reply. I removed the little lock arm (mine has two set screws) and moved it up a little bit so it does not contact the RA slow motion knob when I move it around. However, when I tighten up on it, it still won't stop the motion, and sounds just a little different and feels a little rough. My quess is that the lock ring on the inside is loose. So, I would be glad to get your further instructions. Connections here are not the greatest, but an answer here or via a PM will work. If you have a link to a picture, that would be great. If not, I am a bit handy and know where I can get some basic tools if I need to. Thanks

....about 2 hours from Manila, PI....

#4 Brian Risley

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Posted 27 January 2013 - 09:19 PM

Without pictures of your exact base, I can only go on ones I have access too (Original OT and a Powerstar)
First thing is to get the base apart. The top cap in the middle of the fork should be removed. If there is a screw there, then remove it and see if the base can be lifted off (this was how older models came apart). If it can't then check the very bottom of the base, there may be a nut (possibly with a threaded hole in it) that should be removed. This then should allow the base to be separated. (May need one to hold the base, one to hold the forks.
Once this is separated, look for 3 or 4 screws holding the gear assembly to the central hub (they should be toward the center, there may be screws holding the gear assembly together that are further out, without seeing yours, I can't tell for sure.) The gear assembly (both bottom drive and top adjustment gears sandwich the RA Setting Circle. The gear assembly should then lift out and you can see the RA slow mo gear and there should be a plate (possibly Nylon) screwed in covering the RA Lock Shaft. This is what you are pushing against the top part of the gear plate to lock it.
This link has a great disassembly break out and shows the plate well.
You don't have to take off the fork arms/OTA. Just work over a padded area to set things on. The gear area can be greasy, so don't do it with the fine towels! :)
Hope this can help you ID what is wrong.
Brian

#5 rolandlinda3

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Posted 28 January 2013 - 01:46 AM

Thanks, Brian. Will look at the link and your instructions. May try to go into it tonight. If somethinng looks really strange, will relay a question or two.

#6 rolandlinda3

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Posted 29 January 2013 - 04:52 AM

Thanks, Brian, for the link and tips. I got it apart just fine; took grease off some places it should not be; reassembled but things seemed a little off so took it apart and reassembled again. In the process, I tightened the screws on the nylon pad (they were a little loose). It seemed to work fine but in the process of moving the OTA back and testing it again on the tripod, the lock won't hold again. I will try once more and see if some grease got on the pad again or if something else looks strange. I did not notice any crack in the pad or too much give but will check. Hopefully, success will follow. Will post a result.

#7 rolandlinda3

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Posted 29 January 2013 - 08:57 PM

In case anyone tries this, Brian is right...it is not too bad of a task, but it does take a little practice. The surfaces of plates inside the base are a bit touchy...some want a light coat of grease, some do not. The trick is to make sure that the ones that do not--like the face of the plate that is pressed by the RA lock on a nylon piece--must be absolutely free of grease, or it slips. Second, there is a bit of slop in the central bearing cages, so when I tightened the screws that hold the bearing assembly on the first 4 tries, I simply lined everything up and tightened. That is not good enough. You have to make sure that teh gears for the RA lock fully engage the larger metal plate with teeth. I did not...until the 5th time. So when the screws are barely snug, I had to lift up on the assembly a little bit then tighten to make sure the brass teeth for the tiny RA lock are fully engaged with the larger metal plate. Then, and only then, was everything smooth and worked properly. In the end, as I have said in several places, the old classic C8s are just wonderful. The design is not rocket science but done well, you can repair them, and the optics are well known. This one is in a school in the Philippines; another will go to Mexico; another we use for training. If I could get 3 more today at a really good price, I would do it, because places we go have nothing of the kind, and they can deal with this scope with some training. Regards.

#8 Geo.

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Posted 01 February 2013 - 10:01 AM

9V sounds like a Celestar 8. Subscribe to the CeleStar_8_users-subscribe@yahoogroups.com
Teardown phots there.






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