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Anyone with a LXD75 "Motor fault" message?

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#1 Loren Toole

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Posted 26 March 2011 - 07:15 AM

I purchased a used LXD75 with GoTo about five months ago, which seemed to operate well using a 12 volt jumpstart battery... until mid February following a severe cold snap. The mount is permanently mounted on a pier under my dome, so it rode through the cold (-18 degrees F for two nights) outside. Then, I began to get weird slewing motions around the pier one night, then finally a "motor fault" message on the handbox.

After some testing indoors, I discovered that the mount works just fine if it is operated with a 3 amp regulated 12 volt AC-DC supply, but it continues to report the "motor fault" mesage on my battery pack.

My conclusion: the battery is delivering a significant voltage dip to the mount when slewing is enabled, causing the controller to go haywire. Just for reference, it pulls about 0.7 amp current if both motors slew, I'd guess for a weak battery, this is enough current to cause a 2-3 volt dip.

My question: do any LXD75 owners experience this problem? Obviously I am trying to avoid getting Meade into the repair picture if at all possible...

#2 KWT

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Posted 31 March 2011 - 09:43 AM

If memory serves, the only time I have received the "motor fault" message, is when my DEC motor was under strain due to over tightening the DEC gear mesh. This doesn't sound like your problem, just my 2 cents ;)

#3 jrcrilly

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Posted 31 March 2011 - 09:52 AM

After some testing indoors, I discovered that the mount works just fine if it is operated with a 3 amp regulated 12 volt AC-DC supply, but it continues to report the "motor fault" mesage on my battery pack.


The "motor fault" message means that it tried to move a motor but the encoders didn't report the correct amount of motion. If it works with one supply but not with another that indicates that the decoder adjustment is correct for one source but not for the other. The "calibrate motors" routine sets the comparators for the voltage being supplied and should make it work correctly - but you still need to wonder why the battery isn't supplying the same voltage as the power supply. The battery should be at least as stiff (low voltage drop) as a 3 Amp power supply. The battery is probably gone.

#4 Loren Toole

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Posted 01 April 2011 - 08:22 PM

John
Yes, your explanation makes sense, I did not Calibrate Motors prior to this problem but swapped HBX, which compounded the voltage problem, no doubt...

I'm now anxious to reconnect everything tomorrow and verify that it works. I've seen a number of cryptic comments from LXD75 owners on forums suggesting that Calibrate Motors is essential. But I've learned my lesson on this one, thanks again.

The battery stiffness issue could also be at play here, but I'm betting Calibrate Motors can adjust. My battery is 9 amp-hours capacity, if the 10 D-cell pack works on this mount, I'm sure the larger battery is probably not the cause. So, the voltage dip may not be out of range after all... lesson learned.

Loren

#5 Loren Toole

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Posted 04 April 2011 - 08:14 PM

OK, none of the ideas suggested in this thread worked, including my idea that the battery was causing voltage problems. "Calibrate Motor" still resulted in a RA motor fault message. I've eliminated nearly everything as a cause EXCEPT for balance on the RA axis. Of course I didn't think of this issue until I had re-mounted, tested then de-mounted all of the electronics from my LXD-75. Then I moved the electronics to my shop, plugged in my 3 amp AC/DC 12 volt supply and.... everything worked.

The reason that balance became a possible cause is because I noticed (after removing electronics) the RA axis counter weight was misplaced, causing significant imbalance. Is it possible that axis balance alone could cause a motor fault?






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