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LX-90 8" Mount won't slew right!

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5 replies to this topic

#1 redballoon

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Posted 08 December 2019 - 07:57 AM

The last time I used the telescope for visual purpose was about 2 months ago. Haven't been using it until today because it's been raining in my area for the whole 2 months. When it got clearer last night I decided to bring my scope out and look at the moon. But suddenly the mount won't slew to the right. Both manually and tracking. Anyone can guess what's the problem here? I'm so ****!!

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#2 pyrasanth

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Posted 08 December 2019 - 08:53 AM

Do you have freedom of movement on both axis moving by hand?

 

I would remove all the pay load and counter weights and check to see if there is any obstruction prevent movement of the axis in the desired direction. Sometimes a bad balance can cause this issue as the mount's motors can't overcome the effects of gravity.

 

If you can move by hand then your investigation needs to look at the motors, software and ultimately the electrics/electronics.



#3 OzAndrewJ

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Posted 08 December 2019 - 03:25 PM

Gday Redballoon

As long as the axis is free, that is a classic symptom that the PCh mosfet that drives the motor has blown.

Normally a visual inspection shows a burn mark or a pimple in the casing.

Unfortunately it is a very common failure mode, ( and there are lots of threads on it )

That said, it normally easily fixed if you have access to someone who can work with surface mount components.

 

Andrew Johansen Melbourne Australia

If you do a forum search using the keyword "Vishay", you will see several threads on it here

plus there are lots of threads on the defunct Weasner site

http://www.weasner.com/etx/menu.html



#4 redballoon

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Posted 08 December 2019 - 06:36 PM

Do you have freedom of movement on both axis moving by hand?

I would remove all the pay load and counter weights and check to see if there is any obstruction prevent movement of the axis in the desired direction. Sometimes a bad balance can cause this issue as the mount's motors can't overcome the effects of gravity.

If you can move by hand then your investigation needs to look at the motors, software and ultimately the electrics/electronics.

It's an alt/az mount. That comes with the scope when I bought from Meade. I can slew to right, top & bottom. But not right

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#5 redballoon

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Posted 08 December 2019 - 06:38 PM

Gday Redballoon
As long as the axis is free, that is a classic symptom that the PCh mosfet that drives the motor has blown.
Normally a visual inspection shows a burn mark or a pimple in the casing.
Unfortunately it is a very common failure mode, ( and there are lots of threads on it )
That said, it normally easily fixed if you have access to someone who can work with surface mount components.

Andrew Johansen Melbourne Australia
If you do a forum search using the keyword "Vishay", you will see several threads on it here
plus there are lots of threads on the defunct Weasner site
http://www.weasner.com/etx/menu.html

Does this mean I have to get a new PCH MOSFET from Meade? Replace it with the current one?

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#6 OzAndrewJ

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Posted 08 December 2019 - 06:40 PM

Gday RedBalloon

 

The PCh mosfet is a $1 chip that can be bought from electronics retailers

Meade dont deal in anything smaller than the board itself.

Meade do sell boards, but you need to confirm thats the problem first

 

Andrew Johansen Melbourne Australia




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