Meade ETX-90EC slew question

[04Stefan07 (Stefan)]

I recently picked up this telescope to replace my Skywatcher one.

Fantastic little scope to take around to places. One question though.

I was playing around with it yesterday getting used to the controls, etc. I am not sure if I pressed a certain button or what but if I slew either left or right, when I let go of the button the telescope slews anti-clockwise on it's own for about 5 seconds then stops.

Does anyone know what I have done?

Telescope info (including what the hand controller looks like, it is the basic one): http://www.meade.com/manuals/etx90ec/

ETX-90EC picture: http://www.auburnastro.org/etx90.jpg

Thanks!

[04Stefan07 (Stefan)]

Turned it on today and it didn't do it now it's starting to again.

Can anyone help?

[04Stefan07 (Stefan)]

I can slew in either direction but when I let go of the button it slews anti-clockwise for about 7 seconds then stops.

[coldknights (Cathy)]

Hi have you tried computer control so you can narrow it down maybe to the hc or the cable.
Also some info for you to read.

http://www.weasner.com/etx/90ec_comments.html

[bluezanzibar]

Hi Stefan. I don't know what the problem is but I would check out this page http://www.weasner.com/etx/techtips.html on Mike Weasner's site, and read the Performance Enhancements section. I would firstly try training and calibrating the drives and then upgrade the firmware if it's not the latest version. if that doesn't solve the problem then wading through the vast amount of information on the linked page will hopefully resolve the issue for you.

I have an ETX 105 and I found it to be a steep learning curve getting it to function as advertised but when you get them sorted they're great.
PM me if you keep having trouble and Ill render such assistance as I'm able to.

[Barrykgerdes]

The base only controls the motors from the data sent by the handset where all the calculations take place.

It appears you only have the 494 controller which is rather limited and is probably where the problem lies. I have two or three old 494 with various problems. Connection to a computer requires a special cable that takes care of data conversion

If you are serious about using the telescope get yourself a 497 controller. You will love it then. Computer connection to the 497 is more conventional.

Barry

Barry

[AndrewJ]

Gday Baz

The base only controls the motors from the data sent by the handset where all the calculations take place.

Im not sure thats 100% correct in this case.
The motor card PIC does have some local control in the application of backlash, and the timings of the motor control feedback loops.
Ive not heard of the "creep after beep" type effect occurring in both directions tho. Very weird.
Using a 497 type hbx will allow much better control over whats happening.

Andrew

[Barrykgerdes]

Hi Andrew

I have not seen an ETX 90 or ETX105. I have an ETX125. and an ETX70 (bomb)
I suppose I was being a bit too brief in my description of the base. Yes it does have other functions. However I have found the old 494 controllers a bit too simple yet difficult to master. Access to the computer is via the accessories socket at TTL levels I think rather than a RS232 line as in the 497 controller.

I have had trouble with the motor boards from bad connections but this has not caused the symptoms as described

The ETX 70 has all the works in the fork arm and mine broke after a couple of weeks.The picture of the ETX 90 suggests it has the same mechanics. The worm support (plastic) broke because it did not mesh properly with the worm wheel in the base. Getting it all apart was quite a headache needing special tools.

I still have the bits in a box. I salvaged the optical tube, cut off the dec pivot shafts and mounted it in an old DS 2000 series base.

Barry

[AndrewJ]

Gday Baz

The std 90 and 105 are pretty much the same as the 125s
motor cards wise.
The very early ETXs and the very lates ETX-90
have very basic cards, but still roughly functionally the same.

As you note, a special active cable is used
for doing PC to scope rs232 comms,
as with a 494 handbox, there is no rs232 port in the Hbx
so the system fakes the rs232 by going via the Aux port.

However,
None of that affects the motor cards or how they operate
( other than a bit of model/motorcard specific code )
Soo, i am still confused, as if drive training or lash is bad,
you can always get the creep after beep,
but that only (normally) occurs in one direction.
The fact it occurs in both directions still confuses me.

I suggest setting the backlash percentages to zero and then retraining the drives, to see what that does first.

Andrew

[04Stefan07 (Stefan)]

Thanks for the advice.

So it could be either the HC or mount that's stuffed up? I have a NexStar controller from my Celestron 130SLT, would I be able to use that with the Meade to test to see if it is the HC or do I need Meades AutoStar?

Hopefully there's nothing wrong with the telescope .

[Barrykgerdes]

Originally Posted by 04Stefan07

Thanks for the advice.

So it could be either the HC or mount that's stuffed up? I have a NexStar controller from my Celestron 130SLT, would I be able to use that with the Meade to test to see if it is the HC or do I need Meades AutoStar?

Hopefully there's nothing wrong with the telescope .

No. The Celestron is quite different. You will need an autostar 494 or 497

Barry

[coldknights (Cathy)]

I Would NOT put the Nexstar Hand Controller anywhere near your Meade.
Someone in Melbourne might be able to lend you a 497 Hand. controller for a quick 5 min test.

[04Stefan07 (Stefan)]

Originally Posted by Barrykgerdes

No. The Celestron is quite different. You will need an autostar 494 or 497

Barry

I will try and get my hands on a 497 since it has more functionality.

The telescope came with a power supply to plug into a mains but I plugged it into my portable power supply (12V) which worked fine, I thought I might have blown some electronics.