It shouldn't be doing that... (EQ5Pro DEC drive)

[freespace]

A few weeks ago, I bought myself a EQ5 Pro, and was very excited when it arrived and I got it all setup. It was devastating then when I attempted a 3 star alignment, I heard this horrendous grinding noise noise coming out of the DEC drive.

It was an immediate case of power off, and then wonder what happened.

Called up Andrews Communication, and apparently another gentleman had the same problem, and he thinks it is the motor controller not sending the right signals. So as instructed I sent the motor controller box back to Andrews, and sent a new one off another mount in return.

That however didn't fix the problem - the same machine gun staccato grinding noise is still present whenever DEC drive is engaged. This happens at low slew rates (*1) as well as high (*8).

So I took the motor off the mount, took away the plastic shroud, then detached all the gears until the motor should be free spinning, and took the following video:

http://www.youtube.com/watch?v=GdtGL3hM8sg

I don't think it should be doing that :(

I actually switched directions thrice in the video. First time at 0:05 and as you can see, the motor didn't switch direction at all! Second time at around 0:09 it did, and it did too at 0:15.

Clearly something is wrong - the stepper seems to be really really confused at the start and end. Either I had 2 dud controllers (bad timing could account for this), or this motor has a busted winding or two.

I have tried changing cables around (the RA drive is fine), doing a factory restore, still the same thing.

I don't suppose anyone has had this problem or know of a solution that doesn't involve a replacement? Christmas is coming up and I am likely going to have to wait until 2010 to get a new unit from Andrews (who has been very very helpful btw) :help:

Cheers,
Steve

[gmbfilter]

Whats the dec lash like
Is there the movement in the head when yow wiggle the scope, clutch done up tight
There is a tiny difference too tight and too loose there a couple of adjusting allan head screws that push the worm onto the gear
Some good info here!
http://www.iceinspace.com.au/forum/showthread.php?t=37588
http://www.astro-baby.com/heq5-rebuild/heq5-m1.htm

I have set it up a OK during the day and at night when cooler its, gone US.
For a while I replaced fingers with allan keys
You have to loosen the body adjust the worm tighten the body to hold the worm and sometimes its a pain
Could be another dodgy controller too their qa is variable.

[freespace]

Thanks gmbfilter. There is no lash when the clutch is done up tight. It also isn't a HEQ5, so those links don't really help since the assembly appears to be very different.

I don't believe it has anything to do with gears or lashing or any such business. The video is of the motor free-spinning, and it is not right.


Could be. At this point I am inclined to have Andrews send me a new DEC drive and a new controller, just to be sure.

Cheers,
Steve

[AG Hybrid]

Damn, thats the sound of money exploding. I chringed when I heard that grinding. Maybe a lack of lubricant caused a thread to strip? Pretty unlucky if you had two dud hand controllers.

[freespace]

I don't think it is thread stripping - that would cause stuttering, not the motor turning the wrong way. That said a busted winding won't either.

Maybe the pass through in the RA is broken instead.

[bojan]

It is a motor driver (one phase is missing), or one of the windings of the motor is shorted inside or broken.

[freespace]

Fixed it :D :D

Inspired by bojan's comment I thought to hook up the DEC motor to the RA instead, to see whether it works still, since I know the RA is good.

Turn out it does, so the problem isn't the motor, and it is unlikely to be 2 bad controllers, so the left the pass through being broken.

As I went to take the RA assembly apart, I noticed there was a speck of conductive paint on the DEC connector, probably came off the socket. That's when the penny dropped - the fleck was shorting 2 pins, so it was probably shorting 2 adjacent phases together, which also explains why it works with a high slew rate!

I brushed the fleck off, checked other connectors for similar issue, found none, and plugged DEC drive back in - viola! Worked like a charm!

There is a lesson to be learnt here: keep your connectors clean! If I had paid more attention to the connectors, I would have been up and running the first night, instead of nearly a month later!

I bet the skies will be cloudy tonight though... :P

Cheers,
Steve

[bojan]

Glad you sorted it out :-)