TheSkySearchers

Man I got the stupid AVX DEC clutch blues...

After a successful set up on Sunday night with great alignment, I went to slew to my first target and clunk - nothing moved...

Not the RA or the DEC. Switching on/off had no effect eventually I broke down. Once I had reset things to the home position, taken off all the weight I retried. Both moved, but grudgingly with motion in the right direction then significant backlash, then motion again. Muttering quiet curses I packed away.

Last night I sat with the mount sitting somewhat uncomfortably on my lap. Having read several articles I had bought some washers to try offsetting the potential for binding on the Dec balance arm. This did improve the DEC movement until it stopped, why did it stop?



My clutch handle was misplaced enough to jam. This explains some issues I’ve had in the past. I repositioned the handle and made sure it cleared. At this point I took the washer off and low and behold all worked smoothly on both the DEC & RA. The motion was fluid and sounded much better. I think compression from the washer had flattened whatever was binding where the junction is between the mount body & the balance bar.

It turns out that the cup that covers the joint rotates with the DEC motion, but it can bind on the mount body, or as on mine on the non-moving part that surrounds the DEC shaft. That I believe was happening to mine, but the rubbing was hidden under the cup.

So a bit of a lack of quality control to say the least. Tolerances should be checked, and Celestron are aware of the binding issues, even to the point of telling users what washers to use on a brand new mount! If they are that aware they should be solving the problem. As for positioning clutch handles so they ram into the mounts casing - come on guys, you are not trying really, are you.

Still enough growls from me. It all seems fine and working, but it could have burnt out a board or motor fairly easily.

Now to lay a brickwork path around my new scope site. At least I control the quality there

Glad you have managed to sorted out Tony. To think about it I don't believe any of my mounts worked straight out of the box. Always some tuning, modding or fighting glitches.

Bigzmey wrote: ↑Fri Mar 05, 2021 10:29 pm Glad you have managed to sorted out Tony. To think about it I don't believe any of my mounts worked straight out of the box. Always some tuning, modding or fighting glitches.

OK, interesting to know, I may be expecting too much. At least I’m ironing the creases out.

Clear skies Bigzmey!

Good detective work, Greenman. I too didn't realize it's common for mounts to need fidgeting to get them going.

Hi Tony,

I had the same issue with my AVX years ago. Really freaked me out as to what was happening until I saw the marks on the DEC cover. I was actually quite relieved when I saw the marks. I at least then knew then why my guiding was going haywire! I posted about it at the time (not sure if it was this forum or the old AF site).
I have only contacted Celestron support a couple of times and they have been very responsive. You would think that they would have corrected this simple issue though. My AVX is about 3 1/2 years old. How old is yours?

Overall though, I am happy with the way this budget mount performs. Like Bigz said though, some basic tweaks like reducing the tension on the RA axis and cleaning, polishing, and adjusting the axis drive gears really does help.

Thanks for posting. Brought back unpleasant memories!

Hi Jim, I’ve had the AVX just short of a year. This was the worst jam I’ve had, I knew the clutch was hard to move and often very close to the cover when I packed down, making it hard to release. It never occurred to me that it was hitting the cover. Not until I found the video.

I’m a bit reluctant to strip it down as I’m not the most engineering savvy person and I probably don’t have the tools (rather I may have them - somewhere...). I’ll see how it goes now, the AVX sounds and moves smoothly now. Like it did you this perplexed me, why was the mount suddenly going haywire from time to time? I think most of us with our first GEM, even a lower cost one think it will just work out of the box, and the tweaks need come as a bit of a surprise.

Finishing off my new observation spot this weekend (heh, suitably rustic ).

Looking forward to seeing more of your 533 images. Keep well Jim.