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ETX70 some failures

Meade Equipment
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#1 jab.astro

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Posted 19 January 2025 - 02:07 PM

Hi, just landed into CN

 

I've got a ETX70AT a couple of decades and last two years it has been parked

 

Let's see whether I am able to explain the symptoms and some findings.

 

Yesterday I decided to start it up. I connected a 9V power supply to it. When it started up, during alignment it gave a motor failure error. I restarted several times and there was no way. I increased the power supply voltage to 12V using a regulator (since it suggested that the voltage was not enough) and it started to work better, however while it was moving during the alignment I could see that it was having a hard time, and it even stopped. I could not even hear the movement of the motors to maintain the position once a star was located.

 

I decided to continue manually with the tripod without unlocking anything.

This morning when I started it up, the Meade message appears as you can see in the video (https://www.facebook...978394704185663) and then the image fades and it looks like a movement on the display, but the motors are not heard and the remote control does not act.

 

I decided to disassemble it (first time) and I found  the declination motor broken (I already found STLs to print it out in 3D). Also I looked into the pcb and did not find any noticeable in the connections but AUTOSTAR does not work. 

 

I will be grateful if someone can give me some idea how to proceed. I will be searching along CloudNight messages to determine the problem although I am not sure about it.

Attached Thumbnails

  • 2025-01-19 02.07.03.jpg
  • 473985438_1318834172455268_7121030129154202551_n.jpg


#2 OzAndrewJ

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Posted 19 January 2025 - 02:51 PM

Gday jabastro

I dont do farcebook so

What type of handset and what firmware is loaded

( part of the firmware should show during boot )

 

A motor unit fault during align means the motor has been asked to move

and there is no encoder feedback to say it is moving

This could be a staklled motor, damaged encoder or other things

so step by step.

Andrew Johansen Melbourne Australia


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#3 jab.astro

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Posted 20 January 2025 - 01:46 PM

Gday OzAndrewJ

 

Thanks for your prompt replay

 

Once it starts AutoStar indicates : © 03  Meade  [12S]



#4 OzAndrewJ

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Posted 20 January 2025 - 03:21 PM

Gday jab.astro

12S is not something i have heard of

If you can get to the menus, go to the "Statistics" menu to get the ful number

I am assuming you have a 494 ( ie there are no "numbers" on the handset )

If so, there is very little you can currently do, other than try a "calibrate motors"

The handset sends a command to the cards to move the motors and if it gets no feedback

it declares the fault, so at that point, if you have power but no motors move

you need to start tracing signals.

Andrew Johansen Melbourne Australia



#5 jab.astro

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Posted 20 January 2025 - 06:33 PM

Gday Andrew, it is a 494 model how ever I am not able to reach any menu items (is it possible to upload here a video?) you would see that first appears the text aforementioned and thereafter the screen becomes black.

 

When switched on the device the motors does not move at all.

 

Is it possible to get the schematics of the handset and the pcb? it would help me to split the problem in different tests to find out what is the problem.



#6 OzAndrewJ

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Posted 20 January 2025 - 07:11 PM

Gday jab.astro

IIRC, There are some "rough" schematics on the weasner site

but there are a few minor errors.

Attached File  494BUNDL.doc   74KB   4 downloads

A few of us are currently trying to dig into the 494s so we can update the firmware

without needing the Meade code to be working ( but the chips etc must be OK )

Ifyou can make a few pigtails etc, there are other ways to test the CPU,

but for initial testing,the schematics should be OK

Andrew Johansen Melbourne Australia



#7 jab.astro

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Posted 21 January 2025 - 07:11 PM

Gday Andrew

 

Thanks a lot for the document, I will try to understand the schematics in order to be able to check out whether the circuit is ok or not. Currently I am not able to enter the menus,

 

Is there any diode/fuse that could be damage in case of a problem with power source?



#8 OzAndrewJ

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Posted 21 January 2025 - 07:48 PM

Gday jab.astro

No fuse, no diode, no reverse polarity.

Can you make simple RJ plug pigtails or wire harnesses ????

What control panel sockets do you have???

( Looks like a std 8pin for the handset and 4 pin ( Aux )??? )

Unlike the 497s, there are special boot tests that can be run

to test things, incl a handset test.

If you want to try them first, its very easy, but you need access

to the clock and data lines in order to short them during boot

( vs hold down keys )

For the handset "self" test, you need access to the Az clock line )

Andrew Johansen Melbourne Australia


Edited by OzAndrewJ, 21 January 2025 - 07:48 PM.


#9 jab.astro

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Posted 22 January 2025 - 05:16 PM

Gday Andrew, thanks for your comments.

 

I will try to find as much information as possible (schematics and so on) to test Autostar and motors as you suggests

 

Juan, Almassora, Spain



#10 jab.astro

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Posted 23 January 2025 - 11:56 AM

Hi,
  
Attached you can find the sequence of the starting up of Autostar in three pictures ( I can not upload a video)
 
I found an article related to a tantalum capacitor (https://www.cloudyni...or-issue-as494/), could it be this a symptom of a similar problem?
 
Step1: Screenshot 2025-01-23 at 17.47.04.png
Step2: Screenshot 2025-01-23 at 17.47.09.png
Step3: (I switched off) Screenshot 2025-01-23 at 17.47.21.png

Edited by jab.astro, 23 January 2025 - 11:57 AM.


#11 OzAndrewJ

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Posted 23 January 2025 - 03:22 PM

Gday Jab.astro

OK, as it works initially, it looks like your brightness and contrast are set too low.

They start at full values but then drop back when running

When the screen is dark,can you look at it at a grazing angle in bright light

You may need tochange its angle relative to the light, but often you can see

the texts, even tho the LEDs are off.

Andrew Johansen Melbourne Australia



#12 jab.astro

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Posted 08 February 2025 - 05:23 AM

Gday Andrew

 

I found an article related to Tantalum Capacitor (https://www.cloudyni...or-issue-as494/) in which you mentioned about resetting the 494 , how could I get that information to try to bring to life the device? thanks



#13 OzAndrewJ

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Posted 08 February 2025 - 03:51 PM

Gday Juan

If the mount starts and beeps or shows ANY text at all,

then what we mentioned re "recovering" a handbox will not work

as the fault it fixes renders the handset dead ( ie it never shows any text or beeps )

Yours sounds like it is something else.

The method does allow you to investigate the existing code

and test if memory is working etc, but it wont be a "fix", just a means for investigating.

To do it requires a third party app ( free ) and the ability to connect wires

to the clock and data lines in the handbox.

This can be done several ways, but you would probably need to make up an adapter

of some sort. Very easy if you have the gear and play with this stuff al the time,

but otherwise, might need some help to make the bits

 

Andrew Johansen Melbourne Australia



#14 jab.astro

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Posted 08 February 2025 - 05:01 PM

Gday Andrew, thanks for your comments. Yes indeed, it shows fulltext one second and thereafter it leaves the unit in an undetermined state. I removed the tantalum and verified, and also replacing just for testing with a electrolitic capacitor but the result was the same.

 

I am trying to find a new autostart 494 as I presume that repairing it will not be feasible. I gather that it is not way to reset the unit using the keyboard (I tried the safe mode but it seems not working)



#15 OzAndrewJ

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Posted 08 February 2025 - 06:40 PM

Gday Juan

I gather that it is not way to reset the unit using the keyboard

If its not working, you cannot easily reset using the keyboard.

Being a 494, there is a way to trigger a reset by shorting cables on boot

but it requires basic code to be working.

No harm trying, but its not sounding good.

Sooo, you need to find a way to short both the Alt and Az clock lines to ground

and then boot the handset.

It will carry out an internal keytest where you are asked topress keys

On finishing, it does a memory protection test

If it gets past that, it puts "StarFinder/Autostar 494" on the LCD

and then resets the EEProm to do a full reset on next boot.

If it doesnt get that far, you may have damaged FLASH

and the third party app can check for that, but again, you need direct access

to the clock and data lines to do that.

Andrew Johansen Melbourne Australia



#16 jab.astro

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Posted 08 February 2025 - 07:08 PM

Gday Andrew,

 

thanks again, is there any document that could explain where  and how to short Alt/Az clock lines to ground? and which are the clock/data lines?

 

Juan



#17 OzAndrewJ

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Posted 08 February 2025 - 08:18 PM

Gday Juan

There are lots of details on the port and handset pin functions

Ref attached piccy of a port that the 494 cable would plug into

( ref the panel port, not the Hbx port )

https://www.cloudyni.../#entry12220506

From that you can tell what pins do what

 

Another user made up a simple remote power supply

using a single RJ45 socket for this sort of work,

and others who had older mounts with exposed Alt and Az connectors made pigtails

https://www.cloudyni.../#entry13806347

Whatever way you go, you MUST be ultra careful not to get the polarity wrong.

Check 3 times then check again

 

Andrew Johansen Melbourne Australia


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