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628 Drive Problems

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#26 apfever

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Posted 27 December 2012 - 03:27 PM

This is a back tracking. One thing you need to be sure of is that the RA shaft is rotating in the mount housing smoothly, freely, 360 degrees, no binding, no strain for the clutch/drive. If the shaft does not have propper rotation, don't expect the drive to run it correctly. I won't get into doing this here, but if it needs to be fixed then your into stuff like this:

#27 planet earth

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Posted 28 December 2012 - 04:39 AM

Thanks for posting the pics and the link Neil.
Most helpful.
Sam

#28 Atl

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Posted 07 January 2013 - 08:31 PM

I found the issue and partly resolved the it. The drive motor is gunked up. I soaked it in wd40 while heating it with hand warmers then ran it for an hour with no issues. I am not sure this fix will hold up, but these motors were not made to open up. Any suggestions? However it is now running.

#29 dgreyson

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Posted 07 January 2013 - 10:54 PM

WD 40 will evaporate and the dry film wont keep the old grease in suspension. Soak it in a good quality gun oil instead that wont dry out.

On stuck motors, as a last act of desperation on a sealed clock motor that wont turn I have a procedure I use to get them working again. synchronus motors use a thick grease on the gears and when its sitting for years not in use it eventually hardens into a solid concretion and the motor is stalled dead. To free a stuck sealed synchronus clock motor I take a decimal size drill bit, available at harbor freight, or any wire drill bit just so its very very small and drill a hole in the side or bottom near the edge away from the shaft. Too big a bit and you get metal chips in the works. Drill just enough to make an opening you can insert oil into, dont plunge the bit down thru the gears. next, use an Ink cartridge refill syringe, Insulin syringe or any other sorts of syringes that have a needle to fit in the hole you made. you can use even pen oilers that you could refill, those are readily available, and alternately squirt warm oil in and shake it around and then turn it hole down and squirt air in to blow out the dirty oil and any metal filings. if you use a small enough bit, the filings are small and insignifigant. repeat untill it comes clean. The old grease is like candle wax but it eventually will soften up. After it's clean put some oil back in again.

Plug it in and look at the window thats on most motors to see if the rotor is moving. If its still stopped, pry up the tabs on the plastic window and use a tooth pick or a needle to manually rotate the rotor without bending it. just push it to give it a start and eventually it will take off if the grease is soft enough or washed out. put the window back and bend the tabs to keep it and keep it running and watch it a few hours till you know its ok. Sometimes I have to work it with oil and pushing the rotor for awhile but eventually it will run. Last, clean off the hole and plug it with a smear of silicone.

Anyhow, thats what I do. put a piece of broomstraw on the gearshaft with a dab of wax and you should see it move eventually. If the rotor is moving but the shaft is stopped, you have a gear thats worn down, maybe stripped.
Better to replace it with a new motor.
It's possible to desolder the baseplate with a propane tourch and solder wick and xacto knives to prise it up but usually the motor is too worn out to do anything for it unless you can move a gear up a shaft to bear on an unworn part of the gear. Never had much luck doing that.

#30 Atl

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Posted 08 January 2013 - 08:16 AM

Great ideas. The drive will turn it is just temperature sensitive. I bet soaking it in Breakfree would do it.

#31 rdandrea

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Posted 08 January 2013 - 02:34 PM

After positioning the bushing for end play, I installed the retaining bolt with just a touch of Red Locktite on the threads



That "retaining bolt" is actually how you adjust the end play. The oilite bushing ought to move relatively freely in the hole that's bored for it. It's the pressure of the "retaining bolt" that adjusts how tightly it presses on the worm. Red loctite might make future adjustments difficult.

#32 planet earth

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Posted 09 January 2013 - 04:04 AM

Great ideas. The drive will turn it is just temperature sensitive. I bet soaking it in Breakfree would do it.

I hope it works out for you.
I was fortunate to find a new RA motor for $20.00 and about $20.00 shipping by posting a want ad on Canada Wide Astro.
Surplus shed use to have them and Bill Vorce (Telescope Warehouse), but I believe they are now both sold out. Worth checking out though in case they get any more.Posting want ads can really turn up some fairly rare ATM stuff.
Sam






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