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Meade LXD75

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#1 DougW

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Posted 17 March 2009 - 09:12 AM

help!! on my LXD75 i have noticed that there seems to be alot of play the gears on both the DEC and RA motors. I can push on the scope and it will move 16th of a inch on the RA. DEC is not as bad, but it does have some play. Is there any way to correct this? Or am I just going the have to adjust for it? I've done the "train drive and the PEC update" with no luck.

#2 Eddgie

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Posted 17 March 2009 - 10:13 AM

If you can move it with the clutches locked, then the most likely cause is that the worm gears are not adjusted properly. The two leading causes are end-float in the worm itself (Not likely, but possible), or the worm engagement to the worm gear (most likely).

To do the adjustment on the LXD-75 (I don't have an LXD-75, but I have an LXD-55 and it looks similar to me), you have to remove the motor housings.

When you remove them, the spur gear that stays on the mount identifies the worm drive shaft. You can see that there are a couple of hold-down screws, and a travel screw (If I remember properly). Basically, you loosen the hold down screws and press the housing towards the worm gear so that the worm teeth engage. It might be necessary to back out the travel screw. Press the worm housing up so that the worm is in contact, then tighent the hold-down screws with light pressure.

Now, you use the travel screw to push the worm housing away VERY slightly so that there is a TINY amount of play.

Rotate the worm through 180 degrees of the worm gear (full east to west horizon) If at any time, the movement becomes STIFF, then that indicates the worm gear itself is eccentric or the shaft it bent. Find the tightest spot and use the screw to back it off again so that there is only a TINY amount of play. Of course this will mean that there will be more play at some spots than others.

If the worm has a tight spot in one revolution of the worm (turning just the spur gear), that is an indication of either damage to the worm gear itself (perhaps a burr on the gear)or a bent worm (unlikely).

So, the worm spur gear should turn each revolution smoothly, and 180 degress arc from horizon to horizon of the worm gear itstelf should result in consistent drag on the worm spur gear.

TOO tight is bad.. A bit of play is better than trying to get the worm too tightly engated with the worm gear.

This is not a hard adjustment, but it is tedious.

This will also be a good opportunity to check that the small set screws that hold the spur gears are tight, and that the teeth of these gears meshes fully.. Slack here shows up when you use the handset and there is a delay when you reverse directions.

But if your problem is that there is play when you MANUALLY move the tube, that is usually in the worm to worm gear engagement.

#3 yock1960

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Posted 17 March 2009 - 10:22 AM

Take a look here:

http://www.thestarde...enance_101.html

There is also a Yahoo LXD75 group.

Good Luck!

Steve

#4 DougW

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Posted 17 March 2009 - 04:15 PM

thanks alot Eddgie and Steve, I'll do the maintenance and see if that helps

#5 David Pavlich

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Posted 17 March 2009 - 09:33 PM

I've had mine apart and polished everything up and put some good lubricant on the gears. You'll never get all of the wiggle out of the RA and Dec. In order to do that, it becomes too tight and as Edgie mentioned, that is not good. I've spent a lot of time tinkering with the lash. It's better than when I bought it, but it's a $500 mount and acts like one. For my purpose, grabn'go and outreach stuff, it's a wonderful mount.

David

#6 DaemonGPF

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Posted 17 March 2009 - 10:20 PM

Google Hypertune LXD75. There's a rebuild kit that might help.






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