LX200 Refurbishments

• Remove the whole LX200 motor / gearbox / slow motion worm assembly by removing the two M4 socket head bolts attaching the base plate to the mounting.
• Remove the back plate of the gearbox by undoing 4 screws.
• Undo the cross head screw holding final nylon gear onto the slow motion shaft. You will need a tommy bar to go through the hole cross wise through the slow motion shaft (located on the other side of the worm) to stop the shaft rotating. Carefult when you do this because on the RA this is has the sensor magnet in place.
• Prise off the nylon gear. The shaft it is on is either splined or 'D' shaped.
• Undo the four small countersunk bolts holding the gearbox front plate onto the worm bracket.
• The RA and DEC worm brackets are now ready.
• Remove the Meade front panel connector plate and the main circuit board. Wrap in antistatic bags and dispose of on Ebay!

DEC AXIS The DEC motor assembly is on a bracket that replaces the upstand holding the spring. This holds the motor on the correct place. Two new M3 x 16 cap head bolts secure the Meade bracket to the new motor brackets. The slow motion shaft needs a flat filed to take the grub screw on the new pulley. There is a button head screw 8-32 0.5 inch to screw in the end of the shaft to effectively extend the shaft and provide a more stable base for the pulley. Add the pulley and line up the belt with the motor pulley. Use the side adjustment three bolts to make the belt taught to reduce the backlash. Do not do the belt up excessively tight, it will stall the motor. That is it. Re-attach the bracket to the casing and adjust the worm backleash as normal.

New DEC Components

Brackets in place >

RA AXIS The RA axis rebuild uses a new plate that is screwed on using the existing countersunk screws. You may have to reduce the screw length by 5mm. This is easy by using the upstand metalwork taken off the DEC. There is one hole which is the same screw thread but needs a countersunk drilled in it to make the screw length deep enough, otherwise you do not cut enough off. Screw the CSNK screw right the way in and use a hacksaw to cut off most of what is on the other side. File the end at 45 degrees then it should come out without difficulty (no deformed threads). File a flat on the slow motion shaft for the grub screw on the pulley. Screw in the additional 3-32 0.5 inch screw which provides a shaft extension to give a better base for the pulley to work. Attach the pulley and adjust as per the DEC. The motor slides to get the tension in the belt, then do up the motor screws. That is it. Re-attach the bracket to the casing and adjust the worm backleash as normal.

Modifid RA Bracket

Motor Mounted

FINISHING OFF
Check the tightness and adjustment of the gears. Power up each axis in turn and check that the motors operate smoothly without binding. Fit the front connector plate and plug in the internal motor cable to the RA motor. Plug in the internal cable to the 3 way socket for the periodic error to function. Everything should now be done.

The motor cabling to the drivebox is identical on each axis meaning it is easy to diagnose any faults that may develop.

The final slew rate depends on the load and how good your balance is. This can be adjusted afterwards and should be at least a degree per second.

Comments to Alan Buckman at AWR Technology.