ETX-60, ETX-70, & ETX-80 USER FEEDBACK Last updated: 20 November 2008

This page is for user comments and information specific to the Meade ETX-60AT, ETX-70AT, ETX-80AT-TC, and ETX-80BB. Additional information is available on the ETX-60AT & ETX-70AT Announcements page. Comments on accessories and feedback items appropriate to other ETX models are posted on other pages. If you have any comments, suggestions, questions or answers to questions posed here, e-mail them to me and I'll post them. Please use an appropriate Subject Line on your message. Thanks.

Subject:	RE: EYX-70 broken part
Sent:	Wednesday, November 19, 2008 13:41:46
From:	John Bowen (biggity_bowen@hotmail.com)
Thanks for the info. Half a twist too much and very frustrating....

Subject:	EYX-70 broken part
Sent:	Friday, November 14, 2008 08:22:02
From:	John Bowen (biggity_bowen@hotmail.com)
Hello, after all the repeated warnings in the manual not to, I have
tightened my vertical lock too far and broke the piece. Meade has none
of these anymore and has no part that they currently have on hand that
will cross reference to the ETX70. Do you have any idea of who might
have surplus from parted out ETX70 or am I stuck trying to bond the part
back together. It is broken just as the threads meet the disc.

Thanks, John

"I'd like to be a jellyfish, 'Cause jellyfish don't pay rent." Jimmy
Buffet - Mental Floss

Subject:	I have a Meade ETX-70at
Sent:	Wednesday, November 12, 2008 10:14:54
From:	Nealy Thomas (nealythomas@yahoo.com)
My employer has a Meade ETX-70at and it was recently dropped during a
move.  He would like to get it to someone who could look it over to see
if there was any major damage.  Could you suggest anyone who could
repair it?  Thank you.

NEALY 

Subject:	question
Sent:	Sunday, November 9, 2008 05:47:44
From:	Marco {Stojnci} (s52sk@yahoo.com)
Friend of mind has just buying Meade ETX70at in Italy. There is now
italian fimnware on autostar.
How can now he change from italian to englisch language??

Regards Marco
 
Marko Vidovic
http://www.kasiopeja.com

Subject:	re: ETX 80 will not rotate counterclockwise...
Sent:	Saturday, November 1, 2008 10:40:26
From:	richard seymour (rseymour@wolfenet.com)
You wrote:
>  Seems kind of odd that it would turn in one direction
> but not the other though.

Not really... the Meade systems use an H-bridge to drive
the motors... if one of those 4 transistors were to die,
then it would only move in one direction.
In an H-bridge, the motor is the horizontal bar of the "H",
and each of the 4 legs are a transistor.

If you think of it as:
+++++++++++++  (+12v)
(a)       (b)
+-(motor)-+
(c)       (d)
-------------  (0v)

When transistors (a) and (d) are conducting, current flows from
the +12v at the top, through the motor (left to right) and down to the 0v.
When transistors (b) and (c) are conducting, current flow from
the top, through the motor (*right to left*) and down to 0v.
It's the "left to right" and "right to left" current reversal which
controls the direction of the motor's spin.


I've attached a diagram of the DS family of telescope's
motor card (ignore the red marks, they're for modifications.)
This schematic was posted by "alpeterus" to the Yahoo "Roboscope"
group back in 2004, and is/was the easiest for me to locate.
Its original source appears to be one of Meade's patents.

The final "drives" to the motor are a pair of Power MOS FETs.
On that DS card, they're SI9933 and SI9936
Fairchild Semiconductor also makes then as the NDS9933 and NDS9936
(there are two MOS FETs in each package, so two physical chips on
the circuit board provide a total of four transistors).

The problem could also involve the transistors labeled as
"Q3" and "Q6", which serve to drive "the other half" of the
H-bridge legs.

good luck
--dick


Click for larger version

And:

From:	mrcarney@embarqmail.com (mrcarney@embarqmail.com)
Hi Mike,  I ended up taking the ETX80 apart to get alook at the circuit
board. On regular battery power or 12V the behavior was the same even
without any load on the motors.  Basically not even a peep from the
motor with left arrow.  Another reader of your forum emailed me a
schematic of the board (Thanks much R.S.) Now I just need to correlate
the drive to a particular set of drive mosfets and work my way back to
isolate the faulty component.

Thanks for your help and the forum for questions.

Regards,
Mike

Feedback Archives

Check the Feedback Archives for previous editions of the User Feedback pages.

Go to the ETX Home Page.