Tracking Vibrations in Meade LX90's

[renormalised (Carl)]

I don't know if anyone here with LX90's is getting the same sort of problem, but every now and then when I'm tracking an object, I keep getting this annoying whir in the DEC drive and a slight vibration which you can see in the ep'. It may also be in the RA drive, but it's hard to tell. Best to work on one at a time. Anyway, I've been through all the forums at Meade and elsewhere and it seems to be a recurring problem with the LX90's made for the last few years. Now, whilst I could send mine back to Bintel and have Don and the boys ship it back to Meade for repairs, the thought of having to repeatedly ship scopes back and forth...which has happened to quite a few customers...is not something I'd relish. I'd rather figure it out myself and fix it here at home. It'd be cheaper than paying for the freight. Hopefully, it's not too large a problem to handle myself. It could be one of a number of things...worm gears need adjusting, something loose (apart from the worms) or similar. What I don't want to see is having to get the PCB replaced (problems with the chips).

Meade should go back to their old way of doing things....shipping the parts and helping the scope owners fix it themselves.

[AndrewJ]

Gday Carl

Now, whilst I could send mine back to Bintel and have Don and the boys ship it back to Meade for repairs

If its the problem we tracked down here, it occurred with the first new batches of LX90s with GPSs that came out of Mexico. Mike Weasners ETX site also has a long saga on it as he got 3 bad ones in a row.
If so, it 99% requires the motor cards to be replaced,
( ie it doesnt require a shipping to Meade )
This is a simple exercise for the DEC, but its painfull due to the disassy required. Not sure how easy it is to get at an RA board.

However, there is a good test you can run indoors to confirm it first
If you are a member ot the Yahoo LX90 group,
there is a long thread on it here
http://tech.groups.yahoo.com/group/lx90/message/78903

if not try this test indoors

Stick the scope on a table etc
Set yr scope to AltAz,
turn off the GPS if you have one
( as we want to fake the locn and time )
set a new current location manually to Flagstaff Arizona
reboot scope
Do a normal align
set time to 8.00pm on 01 Jun 2008 with DST ON
Select two star align and let it select its stars
just enter on each one when prompted
When its tracking, select saturn and goto it
It should start ticking ( particularly in DEC ) if the same problem is
there that showed up in the other scopes.

We tested several scopes in the BINTEL Melb store for this,
and grabbed logic analyser plots of the motors / encoders
( it was horrible on the DEC )
We swapped cards between a really really new "non ticker" and a new "ticker" ( using an identical Hbx ) and the ticking went with the card.
Also, the new non ticker had a much later firmware rev on the Motor card PIC ( -07 vs -02 IIRC )
Try that test first and see ( actually you should hear and feel the ticks )
what happens.

Andrew

[renormalised (Carl)]

Thanks for that reply, Andrew. Yeah, the noise I hear sounds almost like the worm gears are grinding against something, like there's something binding in the scope....pretty loud, but the shaking you see in the ep' isn't that bad you lose track of the object you're looking at. It's just a jiggle about. I'll try the idea you suggested. What would be the cost to get it fixed?? Is it possible to DIY the job??

[AndrewJ]

Gday Carl

The problem ( if its the one i described ) manifests in different levels depending on pointing location.
The test i gave is the best one we found for giving "really bad" ticking.

As you note, It may also be dry/badly adjusted gears too
If you just unscrew the DEC knob and remove the cover plate, you can see the DEC worm/wormwheel interface and visually check that.

If it is the PCB version problem, then
As to cost, dunno, you would need to speak to Don
As to can it be fitted DIY, if you are moderately handy, then yes for DEC.
You have to remove the wormwheel to remove the plastic covers
and fiddle out the power panel.
After that, its just unscrew the old PCB and screw in the new one.

Andrew

[renormalised (Carl)]

If it is dry gears, what's the best lubricant to use to free them up? They'll probably need adjusting at the same time.

[AndrewJ]

Gday Carl

As to grease, dunno the "best"
I use some red stuff that i got with a gear set.
There have been lots of discussion on whats best,
but its not my field. Maybe ask Don what they use if its a local brand.
Also, see how freely the worm carrier pivots
It should be easy to push away from the wormwheel and should spring back by itself.

Andrew

[renormalised (Carl)]

Thanks for your help here, Andrew. I'll let you know how it goes, when I get the chance to do it.