AZ-GTi Mystery - You Have Only One Clue

[Ags]

I am the proud owner of two AZ-GTi mounts, but one is sadly useless. Every second or so it 'ticks' by an arcminute or two. Tracking is fine but the the constant ticking and ensuing vibrations make it useless for visual and photography. The ticking occurs in AltAz mode and in EQ mode when tracking so it's safe to say the issue is in the RA assembly. It is also super regular so its not sticky grease, its something with a pretty precise cycle of just under one second.

I have looked at some vids about tuning AZ-GTis and they look a bit worrying but doable, but the question is - where is the fault likely to reside? Does anyone have any ideas what could be jumping, catching or slipping at a 1-second interval? 

In case anyone asks, the mount is out of warranty so I have nothing to lose!

Edited December 4, 2023 by Ags

[Elp]

Mine ticks too... It's likely to explode soon then.

[happy-kat]

Maybe it's like a bit of swarf in there. I'm going to be doing my RA tuning at some point just still getting my starting position on tracking first. There are lots of videos on the inside. 

Edited December 4, 2023 by happy-kat
Typo

[happy-kat]

I'm going to go in prepared with a sort of washer as a possible fix to reduce friction as I've sticky points where RA movement tightens. I can feel where when moving RA manually by hand with clutches off

[Ags]

21 minutes ago, Elp said:

Mine ticks too... It's likely to explode soon then.

Possibly they become self-aware and try to communicate in morse code?

Edited December 4, 2023 by Ags

[Zermelo]

https://stargazerslounge.com/topic/362613-sky-watcher-az-gti-tracking-noises

 

[Ags]

Reading that thread is a bit depressing.  It looks like I was lucky that my GTi didn't develop mechanical problems until it was a few years old. But it's always had electrical/software issues with DEC runaways while tracking, especially when pointed closer to Polaris. The only way to look at Polaris itself was to switch off the mount. It looks like the issue could come from the following areas:

1. Inside the motor. Unfixable.

2. The gears connecting the motor to worm. Clean, inspect and regrease.

3. The worm. Clean inspect and regrease.

4. The binding of the worm with the RA wheel. Tighten the connection when reassembling.

5. The bearings in the middle of the RA wheel. I'm tempted to say that's unfixable.

Given the frequency and consistency of the ticks, I am inclined to discount 5 - that part moves too slowly to produce the ticks that frequently. 

By the way, I don't actually hear the ticks - I only see them.

[fwm891]

It’s likely to be a wire catching in the spur gear from the ra motor it’s about the only thing moving at that speed in the mount. The mount is east to maintain, there are numerous videos . Definitely a good idea to change the grease to a lithium based paste/grease.

theres a video by astrobloke that’s very good 

 

Edited December 5, 2023 by fwm891
vid added

[Ags]

That's a good tip, and very encouraging too!

[AstroNebulee]

I had this issue too with my first AzGti. Not sure if the timing was the same but I had a ticking sound when tracking and RA axis stiff in parts. I found that the locking ring was to tight and needed undoing ever so slightly and then by adjusting the two grub screws that hold it to adjust the tension. This thread may be of help. 

For the image credit to @TSRobot

 

Edited December 5, 2023 by AstroNebulee
Addition

[fwm891]

AZ-GTi service video 

 

[PhilB61]

Don't these have a spring loaded worm to gear arrangement, is it possible the worm is riding up slightly then being pulled back down by the spring in a periodic manner. Possibly made worse with an out of balance setup or just worn out/displaced grease. 

[Ags]

The GTi is pretty old so I can imagine the worm is riding up and down due to old grease. Can anyone recommend a suitable silicone grease? One video I found recommended vaseline, but I think maybe not... 

[AstroNebulee]

2 hours ago, Ags said:

The GTi is pretty old so I can imagine the worm is riding up and down due to old grease. Can anyone recommend a suitable silicone grease? One video I found recommended vaseline, but I think maybe not... 

I just regreased mine with white lithium grease, no issues and still working fine. 

Lee 

[Elp]

Think I need to do this along with my WO wedge (alt az screws are oddly tight, needs a disassembly to see what's up). Although the azgti is ticking on one side of the meridian the subs are fine so it'll wait until things change.

[LaurenceT]

11 hours ago, Elp said:

Think I need to do this along with my WO wedge (alt az screws are oddly tight, needs a disassembly to see what's up). Although the azgti is ticking on one side of the meridian the subs are fine so it'll wait until things change.

I've replaced the altitude screws on my WO wedge with these:

sourcing map M6 x 44mm Metric Male Thread Knurled Clamping Knobs Grip Thumb Screw on Type Hand Clamping Handle Bolt with Plastic Knobs Black 10 Pcs : Amazon.co.uk: DIY & Tools

makes it easier to use the wedge. I initially put some lithium grease on the original WO screws and it didn't help at all.

also @AstroNebulee made this post :

 

https://stargazerslounge.com/topic/391791-william-optics-wedge-declination-screws/?do=findComment&comment=4219498

 

[Elp]

I don't have issue with the existing screws, they've just become very tight for some reason and I never use the locks. Another issue is the altitude comes to a stop before I'm polar aligned so I have to drop the back legs of the tripod, never had to do this when I first had it.

[Ags]

I'll keep a little photoblog of my mechanical adventures. Firstly my tools:

Torch - to help my aged eyes

1.5 mm allen key - for grub screws

Small star screwdriver - to remove cover

Hammer - to fix it real good

 

 

[Ags]

The internet is wrong. The AZ-GTI cover is held on by 4 not 6 screws.

Already found the problem? Look at the red wire looped through the RA motor gear housing at the bottom...

The innards revealed:

[AstroNebulee]

1 hour ago, Ags said:

The internet is wrong. The AZ-GTI cover is held on by 4 not 6 screws.

Already found the problem? Look at the red wire looped through the RA motor gear housing at the bottom...

The innards revealed:

Hopefully moving the red wire removes the issue for you. Now you've got it open best time to regrease it all, good luck. 

Lee

[Ags]

If I was being scientific I would move the wire, put it back together, wait three weeks for a clear night and test - before attempting any more changes. Life's too short for that!

I can see some swarf in the current grease, so I will clean and regrease. 

On second thoughts maybe I should cut the red wire? Then it won't explode...

Edited December 7, 2023 by Ags

[happy-kat]

Are you going to wipe the grease away or use a solvent?

[Ags]

I think just wipe it away, don't want to use solvent if not needed. I have a degree in Chemistry, and the only thing I really learnt is to not trust chemicals, especially ones you can breath in.

[happy-kat]

Sounds good, I'll do a wipe approach too. Currently rummaging for a suitable bit of plastic recycling I could use to make a washer for the stiff az.

[Ags]

Finished it tonight I cleaned and regreased the RA axis. I left DEC alone as I hardly use it. I took care to bend the red wire away from the RA gears. Put it back together and it still works. Next clear night we'll see it it's fixed.