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12in lx200 hand controller, sudden no N-S

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#1 Stevegeo

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Posted 25 August 2021 - 03:34 AM

Last night set up for observation of Saturn and Jupiter  , about 3 hours  of peeping the hand controller started acting wonky.

No  N-S , but E-W worked... weird. So shut off unit. Went manual for a bit then rebooted. It came back  worked as usual then stopped working E-W buttons again.  The S button has a different feel to it.   Maybe it's me.  After a few retries I gave up and shutdown for the night.

I may ad this is in my observatory, always dry.    One thing else the tracking seems a bit slower then usual N -S.

 

Anyone have any experience with this? Or a fix?

 

Stevegeo 



#2 astrokeith

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Posted 25 August 2021 - 03:47 AM

Sounds like you were working the buttons quite hard?

 

Perhaps the rubber button membrane has got disturbed. If you can open up the handset then it should be a simple case of checking it is flat, and in the right position.

 

Make sure it is unplugged, and you are grounded to avoid static damage.


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#3 PETER DREW

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Posted 25 August 2021 - 04:41 AM

Sometimes the DEC cable connection is improved by disconnecting and reconnecting a few times.  Less than optimal connection can lead to all sorts of unusual activity.



#4 Stevegeo

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Posted 25 August 2021 - 08:50 AM

I will give it a try .

I did reset at least once . And unplugged a couple times .



#5 dcaponeii

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Posted 25 August 2021 - 01:25 PM

See Peterson engineering website for a guide for repairing this common problem on the hand controllers. You can download Autostar Suite and use the HBx software to control the scope through the RS-232 cables. (Ask how I know?? Hehe). But the HBx controller in the MyScope software that Andrew developed is a more convenient alternative.
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#6 MikeBY

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Posted 26 August 2021 - 04:06 AM

These intermittent strange responses to guide buttons that suddenly occur and  power cycles fix at least temporarily are mostly RJ9/11 modular jack connection related. 

Blow out dust gently with compressed air then use a plastic safe spray contact cleaner in the jacks and use the plugs from the cable in and out multiple times to remove oxidation from the bare copper contacts on both the jack and plug.  I repeat the cleaning because that now loose oxide needs to be flushed off the contacts.  If this is a 20 year old scope inspect the handset cable carefully for

Brittle dried wire insulation and brittle locking tabs that don't lock well any more. Same for the DEC motor cable interior to the fork! 

You're well past the expected service life of these standard insulation displacement plastic connectors.

Consider replacing these cables if you see improvement but not full resolution of the issue. 

Next, if you're using a mains fed DC power supply, try changing it.  These devices can generate intermittent noise if their electolytic filter caps are beginning to fail. 

Inside in a few places there are what I call "after-thought" ferrite chokes in a few key spots to try and thwart plugin and power transition spikes from locking up inputs but truth be told the noise filtering on both logic inputs and serial data lines by today's standards is inadequate and it's been a bit of issue all along.  

Closely inspect all electolytic caps for any sign of swelling near their leads. 

The internal wiring is almost all very delicate insulation displacement and those wires are all held by very small plastic ridges. 

Of course handset contacts can have intermittent issues but they are more regular and less random,  seldom fixed by power cycle.

It's noise that glitches up the inputs and locks up the logic in these random episodes. You may need to resort to an O-scope to track it down.  

It's possible firmware can get glitched or if you use custom objects free space can get fragmented too. Usually a reload fixes them.  Be sure you back up user tables if you want to save them.


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#7 Stevegeo

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Posted 07 September 2021 - 04:04 AM

I was up to the observatory last nite ( first time in weeks it seemed) and fired up the scope.

Again E W worked great, sadly no N S,   and I did most viewing manual, clutches loose.    I did notice the DEC knob was stiff , very stiff, perhaps its binding. Even loose..  Anyhow I will disassemble  and look into that.  

Pressing the N S buttons does nothing, no motor noise   , zilch. And usually with my old am/fm/ sw radio on I get at least some interference  when anything moves.... this time even E W didnt bother it.

  I dont use the goto on the autostar, as I prefer to do a find on my own.  I know there at thousands of objects listed , and if I get a better scope, I probably will use that function.  I do have an Autobx unit I bought  and plugged in  but could never get it to communicate to my pad, or phone.  I think it's a connection issue but not sure without digging into it.

I did by the unit used , and sometime in its life the OTA was remounted forward to allow for straight up view without crashing.

I was told when I bought it that it sometimes went wonky on the hand controller  , but never had any issue until now.

  So I'm gonna look now into tearing into this , and swapping my C11 onto the pier for the fall/ winter and the Mead 12 onto the scope buggy I built  so I can figure out what's going on.

 

Any other suggestions for a better fix, bypass... or control would be greatly appreciated. 

And to those that chimed in , thanks.. I'm looking at all suggestions...

 

Stevegeo 



#8 astrokeith

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Posted 07 September 2021 - 04:32 AM

I was up to the observatory last nite ( first time in weeks it seemed) and fired up the scope.

Again E W worked great, sadly no N S,   and I did most viewing manual, clutches loose.    I did notice the DEC knob was stiff , very stiff, perhaps its binding. Even loose..  Anyhow I will disassemble  and look into that.  

Pressing the N S buttons does nothing, no motor noise   , zilch. And usually with my old am/fm/ sw radio on I get at least some interference  when anything moves.... this time even E W didnt bother it.

  I dont use the goto on the autostar, as I prefer to do a find on my own.  I know there at thousands of objects listed , and if I get a better scope, I probably will use that function.  I do have an Autobx unit I bought  and plugged in  but could never get it to communicate to my pad, or phone.  I think it's a connection issue but not sure without digging into it.

I did by the unit used , and sometime in its life the OTA was remounted forward to allow for straight up view without crashing.

I was told when I bought it that it sometimes went wonky on the hand controller  , but never had any issue until now.

  So I'm gonna look now into tearing into this , and swapping my C11 onto the pier for the fall/ winter and the Mead 12 onto the scope buggy I built  so I can figure out what's going on.

 

Any other suggestions for a better fix, bypass... or control would be greatly appreciated. 

And to those that chimed in , thanks.. I'm looking at all suggestions...

 

Stevegeo 

Some more clues here!

poses the question is it the handset or the motor?

Does the dec motor move under any circumstances? You say you dont do goto's but if you try one what happens?

If still no motor movement - then its a motor, wiring, or drive board issue.

 

The handset to mount wiring will be a serial communication, and so a problem here would affect everything.

The fact that its both N and S suggests it isnt a physical button problem.

 

I'm assuming you dont have a computer connection to the scope?



#9 dcaponeii

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Posted 07 September 2021 - 09:42 AM

Download MyScopeStuff from Andrew's website and use his software handbox controller via the RS232 port.  It's probably your hand controller but this would confirm it.  I've been running my 12" LX600 all summer using his software handbox without any further issues while I wait on availability of replacement hand controller for my scope.


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#10 Stevegeo

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Posted 07 September 2021 - 10:34 AM

Thank you . That was going to be my next question..how to bypass the controller completely. Run it off my tablet or laptop with software .. I am looking into the motor issue as well just in case .

Stevegeo



#11 dcaponeii

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Posted 07 September 2021 - 11:40 AM

Thank you . That was going to be my next question..how to bypass the controller completely. Run it off my tablet or laptop with software .. I am looking into the motor issue as well just in case .

Stevegeo

The Meade software (Autostar Suite) has a software handbox as well but I like Andrew's Hbx much better.  The Meade software is old enough that the display doesn't show up on a Windows 10 machine.


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#12 Stevegeo

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Posted 19 September 2021 - 06:24 PM

Something I noticed and something I neglected to ad to my probllem.

Noticed the hand controller gets very warm on the back , rt side as you're looking at screen .. never noticed it before and yet to disassemble. 

 

Second when I bought this the OTA had been deforked at sometime and remounted FORWARD about an inch from the original  position . 

Yes it's out of balance . The reason for the remount I was told was the OTA when rotated would not clear the fork... huh? 

Anyhow with eyepieces (2in)   diagonal , it's way off in balance even without  anything . Mirror heavy . 

I thought of rebalancing with counterweight  on corrector end , then the NS issue came up .

 

Question , would an exploratory disassembly of hand controller be in order to diagnose , then Motor on fork to check for voltage?  And if so what should I look for? Bad caps? Connections, what's most likely .. finally is there a seperate  fuze for RA and DEC motors? 

I have experience in electronics , but would like to hear from someone that's been down this dirt road . 

 

Stevegeo 



#13 MikeBY

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Posted 07 October 2021 - 02:30 AM

Something I noticed and something I neglected to ad to my probllem.

Noticed the hand controller gets very warm on the back , rt side as you're looking at screen .. never noticed it before and yet to disassemble. 

 

Second when I bought this the OTA had been deforked at sometime and remounted FORWARD about an inch from the original  position . 

Yes it's out of balance . The reason for the remount I was told was the OTA when rotated would not clear the fork... huh? 

Anyhow with eyepieces (2in)   diagonal , it's way off in balance even without  anything . Mirror heavy . 

I thought of rebalancing with counterweight  on corrector end , then the NS issue came up .

 

Question , would an exploratory disassembly of hand controller be in order to diagnose , then Motor on fork to check for voltage?  And if so what should I look for? Bad caps? Connections, what's most likely .. finally is there a seperate  fuze for RA and DEC motors? 

I have experience in electronics , but would like to hear from someone that's been down this dirt road . 

 

Stevegeo 

Hi Steve,

Just to confirm..is this a 'classic' LX200 not a LX200GPS correct?
Is the power panel listed as 18 VDC?  
 

One bit of warning.. on the Classic LX200 with the 18VDC power panel, the AC/DC power supply supplied by Meade is crap and should not be used. It's regulation is very poor. I've seen better than 23 volts coming out of them.  On the other hand the 12v to 18v DC to DC step up converter Meade supplied to use with a SLA or car battery is quite well regulated.

Most people will recommend using 12 to 15 VDC power supplies instead of 18 VDC.  It does help reduce the power consumption a bit at the expense of some of the motor torque and slew speed. The torque though also helps tracking. 
 

However, on the Classic scopes the significant issue is with capacitors.  There are 5 tantalum capacitors that are directly across the 18V  power connections on the Front Panel, Handbox, Main Board and 2 motor boards. They should be changed to prevent a fire hazard. These caps were rated 25v and can fail in a Short Circuit mode and cause burn damage.  In particular the handset of the classic scope has a ribbon cable that can be burned or scorched that is a hard to replace part. 

What triggered this thought is that Meade designed the classic handset to use the 5 volt DC regulator's heat to keep the handset warm. :)  It's actually mentioned in the manual.

 

It's a 7805 regulator that when running at 18VDC generates quite a bit of warmth dropping it to a regulated 5VDC output. 

 

But if this is a classic version of the LX200 you definitely should open up the handbox and replace that capacitor and the other 4 on with a 10uf 50v electrolytic cap if it hasn't been done already. You should defiantly check.
It also sounds like there could be a simple contact problem with the rubberized contacts. I think someone actually makes a replacement for this rubber pad.  Search on CN for it.

There are more than a few threads on CN about that capacitor replacement so a quick search will find them or look at my posts. No sense in repeating the details here. It's a job that takes some care, as these layered circuit boards are old and a bit fragile, but best to fix it rather than risk damage.
I've run through it myself so LMK if you have any questions.

Clear skies,

 

Michael.

 

 

 

 


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#14 MikeBY

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Posted 07 October 2021 - 02:50 AM

Oh.. and regarding the "not clear the forks"
The 12" LX200 as supplied by Meade can not be pointed straight down (in Alt-Az) mode for transporting the telescope. The OTA is too long.  It's not a problem in use per se, It's an inconvenience  for transport and storage. When packing the scope the OTA points straight UP and makes scope require a longer storage box and affords less protection to the front corrector plate during transport.

I would suggest that you add some soft weights strapped around the corrector at the front of the scope to re-balance.  Remounting the OTA at the original mounting point is an option but would require much more effort because you would need to perform a physical orthagonal realignment of the forks and OTA .  It also doesn't eliminate the need to balance the telescope on the DEC axis. 
There are also "DEC counterweight" systems that use a mounting rail along the bottom and top of the telescope with adjustable weights to allow for a more precise counter balancing of the system.  Either way the need to balance the telescope on this axis always exists. You are just starting with more weight to offset then most. 




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