MX Doesn't Work

[NilRecurring]

My MX has so far been a bit of a disappointment. While I am very impressed by it's pointing accuracy and tracking it unfortunately keeps throwing up the dreaded "Mount Hit Something or Is Out of Balance" error in both RA and Dec, sometimes in only RA and sometimes only in Dec.

The issue is so severe that I can't even finish a T-Point auto calibration. The mount always gives out the error (in both axes) when the OTA is west of the mount. It almost always happens during the start of a slew or occasionally when it's just to about to arrive at it's given target.

I had to reboot the mount 5 times just to get through a 49 point T-Point calibration.

The error happens only in RA when the mount is just tracking and this error can happen at pretty much any point in the sky. I am not sure what's so wrong the mount. I have adjusted the camstops of both axes. What interesting thing I found was that the camstop pin doesn't go all the way down even if I loosen the button head more or even if I loosen the setscrew (as instructed in some threads on SB forums). Here's a picture of it - this is how much I was able to get it down and it doesn't go further than this:

http://i.imgur.com/FVSz8dS.jpg

Does this seem a bit odd to anyone else here? Both motors also run a bit hot - I'm not sure if that's normal. For what it's worth, I have checked and rechecked my balance countless times. As soon as it throws up the error I check the balance and the OTA always stays put.

I've created a large post over at SB and I'm hoping I'll get a response on Monday but they can a bit slow when it comes to these things. My biggest fear is that I'll have to send the unit back and that'll cost a pretty penny. Here's a video of the error:

http://www.youtube.com/watch?v=AO2Sc...ature=youtu.be

[rat156]

Hi,

You are not alone with this problem, even though SB are not willing to admit there is a problem. A quick look at the posts on the SB forum will show that many MX's have a similar problem. Mine turned out to be the drive belts, they were black and frayed, make sure yours are grey.

Cheers
Stuart

[NilRecurring]

I remember your unit having problems, Stuart. My belts are gray though. I really hope SB comes through - otherwise all I have is a $9000 paperweight.

[gregbradley]

Wow, the PMX is really having some quality control issues. Its a fabulous mount when it works but it is a bit touchy.

The cam pin has 2 threaded screws on either side of them. They are supposed to be 2.25 to 2.5 turns out from fully in. They control the tension.

If you have them too tight you may get stalls. If you have them too loose the gears will slip with a horrible grinding sound.

I am not saying this is your problem but if your motors are hot it sounds like they are straining. Perhaps this is why. At least its worth a check.

Perhaps the error message is not really stating the problem and it really should say it stalled.

SB will come through but its probably going to take some patience. But once all set it is a beautifully performing mount. I wish mine did not have that 3 way switch. Its simply not worth the drop in reliability to be able to loosen the gears easily. Its not like it was hard to do on a PME. So its not really even a feature that is worth it especially when it introduces so much fussiness. Its poorly engineered and needs to be redesigned to be more bulletproof and less sensitive to accurate adjustment.

Greg.

[NilRecurring]

Originally Posted by gregbradley

Wow, the PMX is really having some quality control issues. Its a fabulous mount when it works but it is a bit touchy.

The cam pin has 2 threaded screws on either side of them. They are supposed to be 2.25 to 2.5 turns out from fully in. They control the tension.

If you have them too tight you may get stalls. If you have them too loose the gears will slip with a horrible grinding sound.

I am not saying this is your problem but if your motors are hot it sounds like they are straining. Perhaps this is why. At least its worth a check.

Perhaps the error message is not really stating the problem and it really should say it stalled.

Greg.

Thanks Greg, I'll check the threaded screws on the side. Can they just be turned by hand? Completely agree about the 3-way switch!

Also, do your motors run warm at all?

[NilRecurring]

Greg, I did as you suggested but no dice. The issue still occurs. I also hooked up a amps meter to the mount and measured the current. Whilst tracking, the mount starts from using just 200 mA and then ramps upto 550 mA where the mount gives the error in RA. This happens over the course of 5-10 minutes. I don't understand why the current increases - if I switch to balance mode, the current drops to 200 mA.

[Paul Haese]

I had a similar problem with my PME. It turned out being a dicky cable. It took me a while to find the problem but once I did it I have not seen the problem again. It was the cabling coming from motor that was the problem and it was being moved by other cables and causing a short. Perhaps take a look around the cables and see if this is a problem. Probably a long shot and not even the same mount type but it will most likely have the same motors and the same cable.

[NilRecurring]

Paul, how did you find out it was a short?

[Paul Haese]

It was a process of elimination. I stripped the mount several times (there is a thread here about the issue) and thought it was grease on the sensor at first but in the end I found I touched a cable and the alarm stopped upon reboot. It was more good luck but I found out later it has been a problem in the past. Not sure how much room there is in the MX mount but worth some investigation all the same.

[NilRecurring]

Thanks Paul. Will see tomorrow if I can find something with the wires - but the considering how the current increases on the ammeter I don't think it's a short circuit - otherwise I'd see a huge rush of current. But I'll check nonetheless.

Really hoping SB responds tonight.

[Tandum (Robin)]

If it's a cable connection issue, I highly recommend DeoxIT which you can get from jaycar. It's a 2 part cleaner, the first dissolves oxides etc from the contacts and the second preserves them. Not Cheap though and the spray version goes no where, get the other.

http://www.jaycar.com.au/productView.asp?ID=NS1436

[DavidNg (David)]

Hi, sorry for your troubled PMX. Perhaps one can try to separate TheSkyX issue and PMX hardware issue by slewing the mount by hand control unit without TheSkyX? Good luck

[CDKPhil]

I had this problem with my MX two builds ago.

I never had this issue before, as soon as I installed build 6934, I had the exact same error as you have mentioned. It was nothing to do with a hardware problem.

I posted this problem with a video of the motor running in the balance position to the SB forum. It showed that when the motor was running and then aborted it would stop, then run at full speed in the opposite direction. See this link http://www.bisque.com/sc/forums/t/18...px?PageIndex=1

I also noted that when the mount was slewing to a target it would over shoot and reverse to come back to the target. This reverse was causing the stall.

Now I have the latest build for Mac and the problem has miraculously gone away.

I don't know what caused this error, I do know it was something to do with OS 10.8.2, It did not occur on an older Mac running 10.6.8.

I have been running the latest build and doing a lot of other testing, I have not had one problem. Every thing is back to normal.

I don't know what OS you are using or what build of The SkyX. Install the latest build if you have not already done so.

Cheers

Phil

[graham.hobart (Graham stevens)]

The issue I had was the DEC cable not seated properly- would not synch and then would stall. Check the plugs and tension on the cables.
Cheers
Graham.

[CDKPhil]

If the latest build does not work you could try slowing down the Slew rate to help diagnose the problem. Image below.

If the mount is over shooting the target and going into reverse at full slew speed, a slower rate may help overcome the abrupt change in momentum.

Just a suggestion,


cheers

[Joshua Bunn (Joshua)]

Hows the tension on the grey belts, maybe this could be making the motors work harder than they need to be?

Josh

[gregbradley]

Originally Posted by NilRecurring

Greg, I did as you suggested but no dice. The issue still occurs. I also hooked up a amps meter to the mount and measured the current. Whilst tracking, the mount starts from using just 200 mA and then ramps upto 550 mA where the mount gives the error in RA. This happens over the course of 5-10 minutes. I don't understand why the current increases - if I switch to balance mode, the current drops to 200 mA.

At least that is one variable you can tick off the list. Some good posts here about possible causes. I guess you'll have to make your way through them until you arrive at the actual fix.

Greg.

[NilRecurring]

Took a good look at the cables but they all look OK to me. CDKPhil, I am using the latest TheSkyX build but I am able to reproduce the error without connecting the mount to the PC.

Here's what I just posted on SB: However, here's something else that I noticed today - when using the hand controller I'm moving the Dec. axis and I 'successfully' I end up blinking it's LED the RA axis follows 5 seconds after - without me touching the hand controller or anything else. Why is this? Aren't both motors stopped whenever the errors in either of them?

Even more curious is the following: when I move the mount in Dec. only via the HC and then stop moving in Dec the current consumption doesn't drop down to normal current consumption for tracking. Let me clarify: suppose the mount is consuming 300 mA whilst tracking ONLY (this is with perfect balance). I slew the telescope in Dec via the HC - while slewing the current consumption increases to 600 mA or so. However, once I stop slewing in Dec the current consumption does NOT drop down to 300 mA - it stays at 600 mA or so. Shouldn't it come down to 300 mA or whatever the current consumption is when the RA motor is tracking at sidereal rate?

So if the error happens in Dec., why is the mount indicating it in both axes? And yet, when the error occurs in RA whilst tracking it's the only LED that's blinking. Dec does not blink.

[Terry B]

This all seems very poor for what is a very expensive mount.

[whzzz28 (Nathan)]

Originally Posted by Terry B

This all seems very poor for what is a very expensive mount.

Yes this thread concerns me as the PMX was on my "next to buy" list.
That AP 1100GTO is looking even better now.