Replacement Servo for Nexstar 6/8SE

[DRT]

I have a Celestron Nextar 6/8SE mount that I bought second hand. Most of the time the Alt and Az movement work fine but every now and again the stick, which throws the tracking off by miles. I managed to sort the Alt movement by slightly tightening the clutch bolt but the Az movement is still irratic regardless of how loose or tight the clutch bolt is. I think the problem is with the servo as I cannot see anything wrong with the clutch plates or the metal cogs.

Does anyone know where I can buy a replacement servo?

Alternatively, does anyone have any other ideas of what the problem might be? I noticed a small amout of grease between the nylon bushes and the clutch plates. Would cleaning and re-greasing the whole mechanism help? If so, what type of grease do I use?

Thanks in advance for any help or advice you can offer.

[ronin]

David Hinds is the importer/servicing for Celestron equipment so you could try him first.

Will say I recall reading that he prefers that items go through a dealer/retailer, so you may need to identify one near you suitable.

Start here: http://www.celestron.uk.com/

As an independant there is: http://sctelescopes.com/

[Cath]

Celestron do list a 6SE servo assembly on there website ..

http://www.celestron.com/browse-shop/spare-parts/motor-assy-altdec-for-nexstar-68-se-telescopes

Maybe email them about buying one, letting them know what country you live in ?

[DRT]

Thanks, Cath - good to see these are available - I'll ask RVO if they can get one as they are only a few miles up the road from me.

[rowan46]

as I recall the azimuth  doesn't have a clutch it's driven by a small spur gear onto a large  aluminium spur gear  I had one where the teeth had been munched  on the large aluminium spur in the base have you looked at that to see whether any teeth   have been  damaged

[DRT]

Yes, I stripped the whole thing down, cleaned everything with white spirit and meths, re-greased and oiled the various moving parts and then re-assembled it. The teeth on the large static wheel attached to the base looked fine, as did the teeth on the small brass spur gear attached to the azimuth servo. Now that it is re-assembled it is still slipping and I have now noticed that I can move the mount by hand in the azimuth plane with a horrible crunching noise. I think the brass spur gear might be the main problem but also suspect that the servo has been damaged by spinning around whilst the mount is going nowhere.

When I finished re-assembling it today I was ready to throw it in the bin. At a calmer moment I will strip it down again and check the gears.

[DRT]

I sent the mount back to Celestron via RVO for a diagnosis. Control board and Az motor both need replaced - cost = £350.

I have chosen to pay the £40 postage to have it sent to and returned from Celestron. It is now available to anyone who needs spare parts or a tripod.

Lesson learned: don't buy electronic gadgets second hand.