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LX-200 Acting Up

SCT Meade Mount
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#1 cavedweller

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Posted 05 December 2021 - 09:31 PM

Hello All,

 

I bought a 10" F/10 EMC LX-200 on a wedge this past summer and used it about 5 times since without any issues. But this morning, it acted flaky. I set it up last night and looked at a few things using the Go-to and the direction buttons without problems. I powered it off and left it setup so I could take a look at the comet in the early morning.

 

I did not bother doing an alignment when I came back out because I didn't expect it to find the comet for me. I powered it on and manually centered on Arcturus (physically moving it) and waited to find that it was tracking in RA just fine. I then started using the direction buttons to find the comet, but suddenly it took off north without stopping. I pushed several handset buttons and it did not stop. I unplugged the handset and it did not stop. It stopped when I hit the on-off switch.

 

I powered it back on and manually centered it on the comet. It was tracking just fine until, about 10 minutes later, it suddenly did the same thing without me pushing any buttons.

 

Is this a common problem that has a common fix?

 

Regards,

David

 

 



#2 rubmetoasty

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Posted 05 December 2021 - 09:42 PM

While I do not have an Lx200, my Meade LX90 with Autostar had this issue when I first purchased it second hand, I went ahead and updated to the latest firmware, and it solved that among other issues inherent in the old firmware.

 

I would recommend starting with checking which version you have, and maybe take a look at Michael Weasners website (http://www.weasner.c...star_info.htm)l for some more information and how to get your handset updated to patched firmware as a starting point.



#3 jgraham

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Posted 05 December 2021 - 10:11 PM

Random slews can be a symptom of weak batteries. That might be worth checking.


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#4 cavedweller

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Posted 05 December 2021 - 11:15 PM

Thank you. I will check the website about the firmware. I am using an AC power brick that came with the unit. It is an 18VDC HP laptop unit. I will check its current rating.



#5 carolinaskies

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Posted 06 December 2021 - 09:33 AM

Thank you. I will check the website about the firmware. I am using an AC power brick that came with the unit. It is an 18VDC HP laptop unit. I will check its current rating.

Intermittent power drops cause this issue 99% of the time.  

Be very careful about the older 18v models, unless the capacitors have been upgraded these can have issues running too much voltage.   Also, make sure the Amperage rating of the brick is >2A.  

As an aside, if the weather was very cold, also consider the cords to/from the power supply into the mount. Cold weather can make cords brittle and cause diminished power/shorts to the mount.  

Also, DO NOT hot-plug de-plug the hand control, it is not meant to be removed while powered on and can potentially cause damage to the hand control or mount.  



 



#6 Rydeen 98

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Posted 06 December 2021 - 10:24 AM

I'd stop using that 18V power supply immediately.  It will blow your capacitors and could destroy the hand controller.  There's a post here on CN about several capacitors that could be replaced as the original ones were not up to par for the system voltage requirements and the 18V power supply is prone to power spikes.  I replaced the offending capacitors on mine and found a suitable 16V power supply off an old IBM ThinkPad (you can use any 12~16V regulated power supply with a pin that matches the Meade).   After I did that my old Meade 8 inch EMC worked perfectly for over 10 years.  I've since deforked mine for unrelated reasons so that I could use it on my Atlas mount and be able to swap OTA's.

 

I tried to find the exact forum post that I followed to replace my capacitors but couldn't.  This one covers basically the same information but lacks the diagrams and pictures that I had followed way back when.

 

https://www.cloudyni...-lx200-classic/


Edited by Rydeen 98, 06 December 2021 - 10:37 AM.

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#7 rutherfordt

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Posted 06 December 2021 - 01:22 PM

The OP did mention that he was using an 18-volt laptop power supply (not the original poorly regulated one) so most likely it is fine.  Having said that, I would agree with Rydeen98 that he should change the capacitors to something higher-rated than the 25-volt ones that came in it just to future-proof things.



#8 PETER DREW

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Posted 06 December 2021 - 03:10 PM

This used to happen occasionally on my 16"LX200 despite a good power source and uprated capacitors.  Usual problem was poor contacts on the console to fork arm cable.  Undoing the cable and replacing it a couple of times seemed to return operation to normal. 



#9 cavedweller

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Posted 07 December 2021 - 01:09 PM

Thanks for all the tips.

 

Unfortunately, this needs to be moved to my "projects" list.

 

I will document what I do, but it won't be until next year.



#10 rmollise

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Posted 07 December 2021 - 02:33 PM

Thanks for all the tips.

 

Unfortunately, this needs to be moved to my "projects" list.

 

I will document what I do, but it won't be until next year.

Unfortunately, declination runaway is all too common with these scopes.

 

If you're lucky? Declination cable/connectors.

 

Not so lucky? Motor control board.



#11 Jon_Doh

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Posted 09 December 2021 - 09:32 AM

Just buy a suitable battery.



#12 cavedweller

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Posted 09 December 2021 - 10:01 AM

I am seeing recommendations to run the mount at 12 VDC even though the panel says 18VDC.

 

Doesn't a lower voltage mean that it will need to draw more current to do the same amount of work?

 

I will be replacing the suspect caps; can I safely run it at 18 VDC once that is done?



#13 michael8554

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Posted 09 December 2021 - 12:44 PM

"Doesn't a lower voltage mean that it will need to draw more current to do the same amount of work? "

 

Yes - is that a problem with a mains supply to draw from ?



#14 rmollise

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Posted 09 December 2021 - 01:54 PM

I am seeing recommendations to run the mount at 12 VDC even though the panel says 18VDC.

 

Doesn't a lower voltage mean that it will need to draw more current to do the same amount of work?

 

I will be replacing the suspect caps; can I safely run it at 18 VDC once that is done?

The amount of current drawn will be the same. The problem is that the scope really can't deal with higher voltages.


Edited by rmollise, 09 December 2021 - 01:55 PM.


#15 Sheridan

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Posted 13 December 2021 - 08:49 PM

If it's an LX200 classic the Tantalum capacitors have a shelf life of about 6-7 years. If you have a good solder station it's easy to replace. It'll cost you about 8 to $10 in parts if that. I would replace them before you have an instant like I did were you powered it up and a big flame came out the bottom of the unit. The C2 capacitor in your hand controller would be your biggest concern, if it blows it'll take the ribbon cable with it. As for the 12V power supply versus the 18V, Your slew rate will be slower, however all went on it will run just fine.

#16 E Sully

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Posted 19 December 2021 - 01:42 PM

If it came with an 18V power source it is probably an LX200 Classic.  18V is fine if the capacitor replacement has been done.  Also, never turn the scope on without the hand paddle connected, or disconnect it while powered up.  I have a thread concerning the older classics if you want to check it out.

https://www.cloudyni...-classic-lx200/

My scope had a runaway issue with the Declination that was due to a poor connection with the external declination cable and the pins in the mount.  Once I straightened out the pins to make better contact with the cable connector, it ran well. Sometimes it can be due to 2 pots on the motor encoder board that may need a bit of adjustment. 

In my thread, there is also a link to Clearline Technology which sells some good replacement parts, as well as a small board that aids in getting the 2 pots on the motor encoder boards back in adjustment.



#17 Tom Masterson

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Posted 19 December 2021 - 09:07 PM

If it came with an 18V power source it is probably an LX200 Classic.  18V is fine if the capacitor replacement has been done.  Also, never turn the scope on without the hand paddle connected, or disconnect it while powered up.  I have a thread concerning the older classics if you want to check it out.

https://www.cloudyni...-classic-lx200/

My scope had a runaway issue with the Declination that was due to a poor connection with the external declination cable and the pins in the mount.  Once I straightened out the pins to make better contact with the cable connector, it ran well. Sometimes it can be due to 2 pots on the motor encoder board that may need a bit of adjustment. 

In my thread, there is also a link to Clearline Technology which sells some good replacement parts, as well as a small board that aids in getting the 2 pots on the motor encoder boards back in adjustment.

 

This is correct. There's nothing wrong with running the scopes at 18V once the caps are upgraded. There's also nothing wrong with running them at 12v or 16v. Less voltage only means slower slews. This is the reason Meade upped the voltage from 12v to 18v in the first place. The LX200 series was developed in the middle of the SCT wars, where Meade and Celestron were duking it out with full page, or back cover ads in both astro magazines. It was a war of specs. There were some reviews that mentioned the Meade was kinda' slow moving to target. Speed up the scope to be faster than the other guy, put it in the ad. A different power supply and some different silk screening for the front panel is all it took for Meade to get faster slews.

 

The main issue with the caps was Meade used some unregulated power supplies that could spank the caps with voltage spikes right at their rated capacity when turned on. Running the scopes at 12v left enough overhead where it wasn't a problem. It's hard to know if this wouldn't have become an issue with some scopes over time had Meade kept making running them at 12v through the line's lifetime. Dunno, that's crystal ball stuff.

 

Eventually the caps fail by shorting out, becoming tiny thermite bombs. The problem is, this all happens without any warning. The only somewhat common factor I've read about is it seems to happen more frequently after the scope has been sitting unused for a while. That's when my first cap failed, after sitting unused for a couple months in the winter. I flipped the power switch, the amp meter pegged for a couple seconds and went dead. That's when I saw the magic smoke coming out from behind the power panel. Cap one fried.

 

Even switching out to a regulated power supply isn't a guarantee because there's no way of knowing just how close to failure the cap is. One thing I suspected, and it's only a hunch, is the epoxy or the internal metals absorbs a tiny bit of moisture when sitting which causes further breakdown. I found some research that seemed to support that for early tantalum capacitors. FYI, tantalums have been redesigned so they no longer fail by shorting so nothing wrong with replacing with same, as long as a higher working voltage cap is used. 35v is good, 50v better. Back when my blew there was still a Radio Shack in town so I picked up some 35v electrolytics.  

 

Don't get caught up in the voltage vs amps trap. These scopes were originally designed to run at 12v so all the motors are the exactly same whether the scope is marked 12v or 18v. Meade only made a couple small simple changes in later scopes, one of which was adding some small diodes to try to reduce the danger of hot plugging, which is what you did when you unplugged the handbox under power.

 

Bad GOTOs and runaways can also be caused by the trim pots on the motor boards drifting out of tune. One early symptom is lousy 

GOTOs because the pulses the the software counts to keep track of where the scope is pointing become irregular. Another symptom is the motors when tracking get jumpy or jittery or they sound like they are skipping a beat. If its the pots, this usually happens before a random runaway. If the motors are running quiet and smooth, the pots are probably ok but if marginal, varying ambient temps can push them over the edge.

 

As mentioned above, sudden runaways can be caused by a poor connection at the cables. The first solution is to scrub the plug contacts by holding down the locking tab of the connector and running the plug in and out of the socket several times. Doesn't take much crud to block the signal. You can use a Q-tip and some rubbing alcohol, but beware of leaving a string of fuzz which will do the same thing.

 

I strongly suggest you take this opportunity to change out the caps. You'll also want to go to www.ClearLine-tech.com and get a calibration tool. You may never need it if your pots are good, but if they do drift, it's what you'll need to properly adjust them. I suggest checking the pots with the tool when you replace the caps. You can get the replacement caps there too.

 

If you aren't go to do all the caps at once, do the handbox, power panel, and motherboard. The handbox is the #1 priority because that $2 cap takes out a $70 ribbon cable.

 

Do the contact scrub and see what happens. Mark your calendar for cap replacements. Don't procrastinate like I did - TWICE! I knew about the issue, decided to get to it "later" and the first cap blew. Bought 5 replacements, fixed the 1 and got lazy, left the other four in a drawer thinking I'd to them later, that's when the one in the handbox went and melted the keypad cable. Double dumb. When I bought my second used mount - the LXD650 - that uses the same caps and power supply, I replaced the caps and power supply before ever powering up the mount.

 

The good news is, once the caps are replaced, and you know how to adjust the pots, these mounts are pretty reliable and robust. My 12" is a 2000 model, and my LXD650 is late '90s, and they are still going strong. Not bad for flip phone era tech. It's also funny when I'm at a starparty and doing a GOTO and someone says: "That sounds like a Meade over there!" My reply is: "Yes, it is! and how would you like your coffee beans ground? Drip or pour over?"


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#18 cavedweller

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Posted 19 December 2021 - 10:38 PM

I am tracking and thankful for the many helpful suggestions being offered.

 

I checked and the 18 VDC HP laptop power supply is rated for 2.23A.



#19 Sheridan

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Posted 04 January 2022 - 09:40 AM

This is a bit more expensive but here's another option for you. http://clearline-tec...m/products.html They make replacement boards. This Gentlemen from this site actually makes an autostar/audistar conversion. https://groups.io/g/LX200Astar I sometimes still think about converting it to an autostar.
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#20 deSitter

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Posted 05 January 2022 - 12:37 AM

Hello All,

 

I bought a 10" F/10 EMC LX-200 on a wedge this past summer and used it about 5 times since without any issues. But this morning, it acted flaky. I set it up last night and looked at a few things using the Go-to and the direction buttons without problems. I powered it off and left it setup so I could take a look at the comet in the early morning.

 

I did not bother doing an alignment when I came back out because I didn't expect it to find the comet for me. I powered it on and manually centered on Arcturus (physically moving it) and waited to find that it was tracking in RA just fine. I then started using the direction buttons to find the comet, but suddenly it took off north without stopping. I pushed several handset buttons and it did not stop. I unplugged the handset and it did not stop. It stopped when I hit the on-off switch.

 

I powered it back on and manually centered it on the comet. It was tracking just fine until, about 10 minutes later, it suddenly did the same thing without me pushing any buttons.

 

Is this a common problem that has a common fix?

 

Regards,

David

I would immediately suspect condensation in the electronics. Metal exposed to the sky will get very cold, and if the electronics are not in operation it is not making any heat, and water could form and drip on the exposed circuit boards.

 

-drl



#21 deSitter

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Posted 05 January 2022 - 12:42 AM

This is correct. There's nothing wrong with running the scopes at 18V once the caps are upgraded. There's also nothing wrong with running them at 12v or 16v. Less voltage only means slower slews. This is the reason Meade upped the voltage from 12v to 18v in the first place. The LX200 series was developed in the middle of the SCT wars, where Meade and Celestron were duking it out with full page, or back cover ads in both astro magazines. It was a war of specs. There were some reviews that mentioned the Meade was kinda' slow moving to target. Speed up the scope to be faster than the other guy, put it in the ad. A different power supply and some different silk screening for the front panel is all it took for Meade to get faster slews.

 

The main issue with the caps was Meade used some unregulated power supplies that could spank the caps with voltage spikes right at their rated capacity when turned on. Running the scopes at 12v left enough overhead where it wasn't a problem. It's hard to know if this wouldn't have become an issue with some scopes over time had Meade kept making running them at 12v through the line's lifetime. Dunno, that's crystal ball stuff.

 

Eventually the caps fail by shorting out, becoming tiny thermite bombs. The problem is, this all happens without any warning. The only somewhat common factor I've read about is it seems to happen more frequently after the scope has been sitting unused for a while. That's when my first cap failed, after sitting unused for a couple months in the winter. I flipped the power switch, the amp meter pegged for a couple seconds and went dead. That's when I saw the magic smoke coming out from behind the power panel. Cap one fried.

 

Even switching out to a regulated power supply isn't a guarantee because there's no way of knowing just how close to failure the cap is. One thing I suspected, and it's only a hunch, is the epoxy or the internal metals absorbs a tiny bit of moisture when sitting which causes further breakdown. I found some research that seemed to support that for early tantalum capacitors. FYI, tantalums have been redesigned so they no longer fail by shorting so nothing wrong with replacing with same, as long as a higher working voltage cap is used. 35v is good, 50v better. Back when my blew there was still a Radio Shack in town so I picked up some 35v electrolytics.  

 

Don't get caught up in the voltage vs amps trap. These scopes were originally designed to run at 12v so all the motors are the exactly same whether the scope is marked 12v or 18v. Meade only made a couple small simple changes in later scopes, one of which was adding some small diodes to try to reduce the danger of hot plugging, which is what you did when you unplugged the handbox under power.

 

Bad GOTOs and runaways can also be caused by the trim pots on the motor boards drifting out of tune. One early symptom is lousy 

GOTOs because the pulses the the software counts to keep track of where the scope is pointing become irregular. Another symptom is the motors when tracking get jumpy or jittery or they sound like they are skipping a beat. If its the pots, this usually happens before a random runaway. If the motors are running quiet and smooth, the pots are probably ok but if marginal, varying ambient temps can push them over the edge.

 

As mentioned above, sudden runaways can be caused by a poor connection at the cables. The first solution is to scrub the plug contacts by holding down the locking tab of the connector and running the plug in and out of the socket several times. Doesn't take much crud to block the signal. You can use a Q-tip and some rubbing alcohol, but beware of leaving a string of fuzz which will do the same thing.

 

I strongly suggest you take this opportunity to change out the caps. You'll also want to go to www.ClearLine-tech.com and get a calibration tool. You may never need it if your pots are good, but if they do drift, it's what you'll need to properly adjust them. I suggest checking the pots with the tool when you replace the caps. You can get the replacement caps there too.

 

If you aren't go to do all the caps at once, do the handbox, power panel, and motherboard. The handbox is the #1 priority because that $2 cap takes out a $70 ribbon cable.

 

Do the contact scrub and see what happens. Mark your calendar for cap replacements. Don't procrastinate like I did - TWICE! I knew about the issue, decided to get to it "later" and the first cap blew. Bought 5 replacements, fixed the 1 and got lazy, left the other four in a drawer thinking I'd to them later, that's when the one in the handbox went and melted the keypad cable. Double dumb. When I bought my second used mount - the LXD650 - that uses the same caps and power supply, I replaced the caps and power supply before ever powering up the mount.

 

The good news is, once the caps are replaced, and you know how to adjust the pots, these mounts are pretty reliable and robust. My 12" is a 2000 model, and my LXD650 is late '90s, and they are still going strong. Not bad for flip phone era tech. It's also funny when I'm at a starparty and doing a GOTO and someone says: "That sounds like a Meade over there!" My reply is: "Yes, it is! and how would you like your coffee beans ground? Drip or pour over?"

I have the LXD650 - I love that beast! I did change the 3 caps that take 18v directly from the brick but I still never run it at more than 15v and usually 12v, I don't care if the slews are slow! I swear I think this mount could do 50 lbs. It handles my 40 lb 10" f/4.5 Newtonian fine.

 

-drl



#22 Tom Masterson

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Posted 05 January 2022 - 08:43 PM

I have the LXD650 - I love that beast! I did change the 3 caps that take 18v directly from the brick but I still never run it at more than 15v and usually 12v, I don't care if the slews are slow! I swear I think this mount could do 50 lbs. It handles my 40 lb 10" f/4.5 Newtonian fine.

 

-drl

I debated for quite a while about whether to get the 650 or the 750. I knew the 750 would be super solid and more than enough for my 6" refractor. Alas, I'm not getting any younger and I was realistically looking toward the future where lifting a 50lb equatorial head up onto my pier might get tough. I WANTED the 750, but 35lb 650 seemed the smart thing to do for the long run.

 

I too like the mount, in part because I've owned a LX200 Classic for years and am very familiar with it, but also because the controller is simple to use. Not a lot of button presses to get me to where I'm going. If something isn't in the database, I enter the coordinates directly. Pretty easy.

 

I'll be curious just how long both these old scopes keep going. Will they still be running 10 or 20 years from now? Will I still be running 10 or 20 years from now? Hope so on both counts.



#23 Stevegeo

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Posted 05 January 2022 - 09:12 PM

This is a bit more expensive but here's another option for you. http://clearline-tec...m/products.html They make replacement boards. This Gentlemen from this site actually makes an autostar/audistar conversion. https://groups.io/g/LX200Astar I sometimes still think about converting it to an autostar.

Thanks much for this. My lx200  Meade 12 went  dark on the dec drive one night unexpectedly and I have dreaded redoing the main board ..

Stevegeo 




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