I Snow What You Mean

Ah yes, I have alot of experience fixing probs like this in the LX.
Does the dec access wobble even with the dec clutch locked ??

IF so, turn the scope off, and push the dec slow motion control UP, this makes the worm fully engage the gear, this happens as the tension spring either gets loose or actually contracts in ther cold and doesnt push as hard as it should. If this isnt the problem, describe exactly whats happening and we'll try help.

In my original post, I think "not quite right" was a collosal understatement. Firstly, there were two (!) limit setscrews controlling the engagement of the worm, and the inner one was too tight. Of course loosening that simply led to the problem you described: spring too weak to positively control engagement (I get more compression/less engagement slewing up, and less compression/more engagement slewing down). I've augmented the spring with a second one from the fuse holder in a cigarette lighter plug, but the combined action is still a bit weak (the difference in compression is down to about 0.25mm, but I suspect it needs to be zero).

These remedies have cleared up about 2/3 of the problem. However, I'm still getting vibration through, and you can hear the motor running quite erratically. My ETX produces a bit of a ticking sound when tracking, but it's a fairly regular ticking. The 16" produces a completely random buzz in bursts of about 1/10 second, with 1 to 3 bursts per second. I think it's time for a new motor or motor controller.

-- Jeff.

Hi JeyJey,
I remember seeing something on Mike Weasners ETX site describing a similar problem. Unfortunately I couldn't find the post. I found some advice but I don't think it will be much help, none the less:

Mike here: There can be many reasons for a Motor Fault. Low battery power, extremely low temperature, bad cable, bad connection, dirt on the encoders, not setting up in the proper HOME position, wrong telescope selection. If none of these, do a CALIBRATE and TRAIN DRIVES. If that doesn't clear it, do a RESET, CALIBRATE, TRAIN DRIVES. If you are still having a problem, upgrade to latest ROM from Meade's site. One other thing that can help, especially if the telescope has not been used for awhile: unlock the axes and move the tube by hand from hard stop to hard stop, in both directions, several times. This can redistribute the grease.

The fact that your motor is ticking is not a good sign. It sounds like a broken tooth on a gear or misaligned gears. These are things you wont be able to remedy yourself, so I hope it's something a little more mundane.

Thanks,

Dave P

Dave --

I also remember reading stuff on Weasner's site, but I couldn't find it either. I did find a bunch of stuff on the MAPUG archives, which led to many of the remedies I've tried so far.

I've now got an email into Meade to see what they say. I'm certainly not going to be shipping this beast back to CA -- hopefully they'll be willing to mail me replacement parts (I'm reasonably handy mechanically and electronically).

While this doesn't reflect very well on Meade's quality control, it does give them a chance to shine in the customer service department

-- Jeff.

Jey,
When tou have the declination clutch open, is the tube balanced??, it sounds like the tube is grossly unbalanced,
In my 12" lx200, you can hear it straining if the scope is slew up (for eg) and almost freefalling when slewing down if it is seriously imbalanced.
I've heard of motors chugging and even stalling if the scope goes conpletely out of balance.
the eratic behavour sound like the worm is binding, which i get here if i adjust the worm to tightly.
Also never slew the scope at the full speed, always select the slowest slew speeds when in use, high slew speeds is a motor killer on these scopes.
For best motor life, the tube needs to be balanced from zenith to horison.

Also make sure the motor is not binding with the main cog, irregularities (I've read of) can cause the worm to be loose one minute and too tight the next, this can happen if the main cog hasnt been drilled properly, the central hole not been central, check this also.

Is the scope in polar or altaz mode, polar mode is inherently less atable and is more prone to vibration, but there are simple ways to improve this, especially in the R.A. bearing.

Its a pity you're not near buy, I'd have a good look at the drive if you wanted.

I've stripped down my own RA drive for a problem 2 years ago, it can be great fun.

Dave --

No, the scope is pretty well balanced. It will slowly tilt down (I've got a crayford focuser on the back), but I'd say it's out by less than a pound. It's mounted alt/az.

I've completely backed off the limit setscrew and manually disengaged the worm from the worm wheel. The motor still gives the erratic buzzing sound. I suppose that suggests electronics rather than something mechanical in the motor, but I'm not sure.

I set my max slew speed to 5° on my 8" and 3° on the 16". But I'll admit that it's more to preserve my peace of mind than the telecope's drives. The higher slew speed noises set my teeth on edge

I'm on hold right now with Meade technical support. I spent 20 min on hold earlier, only to have someone transfer me to a voicemail box. Sigh.

-- Jeff.

I hate to (continue to) hijack this thread, but I thought others might be interested in my saga.

After another 15min on hold, the second Meade customer service agent was willing to make sure the guy he was transferring me to was at his desk. He was, and after a brief conversation, given my special circumstances (I bought the scope in the US but then moved to Ireland), he agreed to send me out a replacement motor/worm assembly and controller rather than having to return the scope for repair. Meade pays for the parts and I pay for the shipping.

Entirely reasonable, I thought (well, except for the half hour on hold, but that seems to be the way business is done these days).

-- Jeff.