Last updated: 26 June 2000

ETX-125RA Right Ascension Drive Fix

From: R. B. Ingersoll, M.D. (rbi@indy.net)

First, let me say that your site is a Godsend for any owner of ETX telescopes. I am happy to be able to contribute a few tidbits to help owners of the ETX-125 telescope. Please excerpt appropriate portions of this email to your various categories of helpful hints, if you so choose.

I have owned my ETX-125 since March 2000 and have concluded that (1) the optics are wonderful for a scope to this size and (2) the mechanical aspects of the scope need improvement and finally, (3) Meade needs a better customer support service (an E-mail address would help) and their manuals are terrible.

I have read about your problems with random slewing, and it is my opinion that the Autostar software must be the culprit. I bought a Meade 12volt AC adapter (made in China, and puts out 18V DC, by the way, not 12V), and made the mistake of connecting it to the telescope while the Autostar was ON. The unit blinked, re-initialized and began having problems with random slewing (always straight up), where I never had it before. I received intermittent messages about motor unit failure, yet the drives still worked. Additionally, some of the Autostar menus were now gibberish and unreadable. I reloaded the Autostar software (2.0i) using the strategy you outlined for using a Macintosh computer (thank you, by the way), Virtual PC 2.1.2 and a digital camera adapter. It worked! the random slewing problem vanished, and the menus were restored.

On another note, I recently began having problems with my RA drive, specifically, it would slew to a certain point and stop (nowhere near the hard stops). The Autostar controller would not move it either left or right, but the vertical (altitude) drive worked fine. I called Meade and their customer service dept. suggested that I partially engage the clutch and manually rotate the scope from hardstop to hardstop to spread lubricant. This seemed to work temporarily, but the problem returned. Frustrated, I decided to risk my warranty, and investigate myself. See enclosed pictures. If anyone has this problem with their RA drive or experiences excessive "drive slop", I may have found the solution, but use it at your own risk. The good news is that the fix is relatively low-tech.

(1) open the base plate by removing the three Phillips-head screws, support the plate while removing because the black (negative) wire that runs from the battery compartment to the computer control switch is very short, and fragile.

RA fix

(2) using the Autostar on a slow slew speed (3-5), carefully try the left/right controls. In my situation, the plastic gears of the RA drive rotated fine but the brass worm gear moved only intermittently, and sometimes not at all. I noticed that the final plastic gear which it attached to the brass worm gear has within it, a 3/32" hex (Allen) screw which was loose. It gradually tightened it with the appropriate hex wrench, retesting between tightenings, and the problem was solved. The RA drive it PERECT. The Autostar's GOTO accuracy seems much better also (which makes sense, if the drive gear was slipping)

RA fix

(3) as an aside, also notice in the pictures that there are two Phillips screws with stripped heads holding the RA drive mechanism to the base plate. What's up with that? I have never had the base plate off before and the scope was sold to me from Anacortes (mail-order) as new. I find it difficult to believe that the scope was assembled so carelessly in the factory. I have a sneaking suspicion that someone returned this scope, either to Meade or Anacortes, and it was then resold to me as new. Hmm........

I hope someone finds this useful.

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