some repair on avx, ra motor gears issue, and spare parts request

[Erquy]

hi

it is just to share some experience with repairing my avx: suddenly, i started to have a severe knocking issue with the RA movement: by guiding i could identify it coming periodically, exactly 6 times per 10 min, exact same smooth guiding in between ( i have guiding typically betwen 0.6 to 1.2 rms depending conditions with the avx with either c8 or the wogt81): a big jump in RA guiding in phd, up to 7-10 arc sec, lasting 2-3 shot (2,5 sec each), and corrected.... I unmounted the ra motor and its cover: you find 4 spur gears: 1st very small in white plastic, 2sd one metal (inner part) and white plastic (outside part, in contact with the 1st small one)) the other 2 are in metal. the 2sd one was the problem: it looks a bit like below left picture ( picture from internet, not exactly that one , the black being white, unfortunately i did not take a picture and now it is back in)

the issue it was broken from the metal/plastic to the edge (as illustrated on the right by the black mark)

so i fixed the issue by taking the same part from the dec motor and replace each other. now the problem is on the dec, but at least, with proper PA, i can run several hours imaging without getting on that failure.

of course, i would like to find a a good replacement, but i could not find any of such spare part any where. anybody has a clue where to find spur gear spare part of an avx motor ? (deep space product offer a full ra motor, but i do not need that, only this little inner spur gear). has anyone a broken avx ra motor to offer (or simply the inside spur gear ?)

thanks in advance

[Gazabone]

Good luck with this. Your mount can't be very old as the AVX hasn't been around for that long. For the cost of these things, I would expect a bit better build quality.

[ChrisLX200]

You could maybe just buy a replacement gear - e.g., http://www.motionco.co.uk/gears-spur-gears-c-32_33.html

ChrisH

[Erquy]

thanks. it is 2,5 year old. i guess it has been running some 150-200 hrs in total (setting + imaging time + visual)

[Gazabone]

thanks. it is 2,5 year old. i guess it has been running some 150-200 hrs in total (setting + imaging time + visual)

Shame it's out of guarantee (presumably). A gear should last a lot longer than that!

[Erquy]

ChrisH, thanks for the link, but they do not seem to have the one (double spur gear, the inner part being metal, outside of plastic, it does not seem easy to find)

[ChrisLX200]

ChrisH, thanks for the link, but they do not seem to have the one (double spur gear, the inner part being metal, outside of plastic, it does not seem easy to find)

That is a combined component meaning the large spur gear and small pinion are separate parts. They cannot be machined together in one piece anyway, so you specify both and put it together yourself.

ChrisH

[Ajohn]

You could try phoning Celestron UK. They do carry some spares or maybe be able to get the smaller parts.

Personally if  replacing myself I would replace any plastic gears with brass ones if I could. There are details on the web concerning gear design. These can allow people to  measure the gear, count the teeth and determine what the pitch is. There are some pretty simple  rules for that.

John

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