HELP PLEASE.....Dec problem.

[paul mc c]

Hello all,i went out to use the Meade 12" and the scope has developed a problem.....

I have had a look at the Dec motor block and gears,its a strange one,when i turn the manual nod the gear movements are smooth in both south and north,now when i turn the power on  and use the hand controler the south movement is laboured,especially in the slower slew speeds and there is a definate shuddering,it seems to be mechenical in the gear region or motor rather than electronical.

When the scope is aligned and tracking there is a "jerking"in Dec movement that occurs and at regular intervals maybe every 8 seconds or so,and i can actually see the gears "jerk"which i can obviously see at the eyepiece when viewing.

Any help please would be greatly appreciated.

Thanks Paul

[MARS1960]

If all is fine with gears manually then i can only assume it's electrical, maybe varying voltage or intermittent  voltage breaks due to cables or contacts possibly?

[barkis]

What are you powering the scope with,  is it a  PSU, or batteries. Are the Dec.and  Ra clutches OK, no slippage?        What Meade Model is it?                               Check cables very carefully too, especially the hand controller cable. Bad connections can produce all kinds of oddities. 

[paul mc c]

Hi,it is powered bt the origional 18v mains power supply,there is no slippage in the clutches and it is a 12" Meade lx 200 classic.

[barkis]

Pretty reliable  scope the LX200. It probably isn't  a serious fault, but tracking it down can be difficult.     I would start with  doing  continuity tests on the control cable.                              Do you get any message on the handset when the problem  crops up?                    Meade have an active forum  for the LX Scopes,  search for Meade 4M Forum, there is lots of Info.on the various faults that can crop up.             The Yahoo LX group also can provide much in the way of assistance. Dr. Clay Sherrod  is a mine of information on the LX scopes. 

[paul mc c]

Thanks mate,there was no message on the hand set when it began......when you say continuity tests,how ?

[barkis]

4 minutes ago, paul mc c said:

Thanks mate,there was no message on the hand set when it began......when you say continuity tests,how ?

You will need a Multimeter to test the individual cables running through the Handset cable itself.
Set the Meter to the Ohms scale at it's lowest value, the cable I think has six wires running through it, all different colours, which you can see easily enough.
Connect the probes of the meter, one at each end of the control cable making sure you are contacting the pin corresponding to each coloured core.
If there is continuity through the cable, the meter will read zero, or a very small number. If there is no continuity, the meter will not respond.

[paul mc c]

Just picked up a meter....sorry for the dumbness.....do you mean the cable that runs to the Dec motor or the handset,and is the scope switched off.

[Peter Drew]

Check the drive belt tension, it needs to be reasonably tight. If too loose the belt snatches. 

[paul mc c]

Hi Peter,the scope doesnt have a belt,just gears and motors.

[michael8554]

Hi Paul,

Is the ota well balanced?

I think I've heard this problem before, possibly the spring that keeps the worm meshed?

I would post on the yahoo LX200 forum as suggested.

Michael

[Davey-T]

Have you run it with the cover of the dec drive so you can see what's happening ? turning the knob by hand isn't quite the same as powering it by motor.

You can rotate the worm wheel to a new spot if it's been running in the same place for years it may be worn.

Dave

[paul mc c]

I have seemed to have this sorted,i made a small adjustment to the com pots on the Dec block and the issue has now gone,a big relief as i thought it was something more serious.

Thanks all for the help guys,it was greatly appreciated.