How To Troubleshoot a Meade Telescope Drive Problem

The drive capability on a Meade telescope comes from two DC motors, one for the right ascension (RA) and one for the declination (Dec). Right ascension is the measurement of celestial longitude while declination is a measure of celestial latitude. Working in conjunction with each other, the two motors move the telescope's optical tube assembly (OTA) compensating for the movement of the Earth, allowing the telescope to remain pointed at a fixed position in the sky. If either motor fails to perform correctly, the OTA will not move properly and it will be impossible to keep an object centered within the field of view.

Things You'll Need

• Phillips head screwdriver
• Multi-meter with probes
• Soldering gun
• Rosin-core solder
• 3-volt power source

Instructions

1. Remove the telescope from the mount by unscrewing the locking nut that passes up through the middle of the mount. Lift the telescope off the mount and lay it on its side.

2. Remove the base plate from the bottom of the telescope mount. Each model is slightly different but the base plate can be removed from any model by removing the screws that hold it in place and gently lifting it out of position. The RA motor will now be exposed can be gently approached.

3. Remove the RA motor from the telescope base by carefully disconnecting the two electrical connectors and then removing the two assembly screws that hold the motor in place. Set the multi-meter to "continuity" and connect the meter probes across the two electrical posts on the motor, where the wires are soldered. If the meter reads "infinity" the motor is bad and must be replaced. If the meter shows some continuity on the meter, the motor is fine.

4. Connect the meter probes to the two female pins, where the two wires were disconnected when you removed the motor. If the meter shows no continuity, wiggle the wires. If some continuity is shown when the wires are wiggled, re-solder the wire connections because one of them is damaged.

5. Apply 3 volts of power to the motor, through the two electrical connectors. If the motor runs, reinstall the motor within the telescope base. If the motor fails, recheck the solder connections. Once the motor is reinstalled in the base, turn on the telescope power. If the motor fails to run, the problem is within the motherboard and the board must be replaced.

6. Check the Dec motor by removing the connector cable running from the telescope control panel to the motor connector on the support arm (located on one side of the fork supporting the OTA). This cable contains 8 connectors and each one must be checked for continuity. Connect a meter probe to a connector at one end of the cable and then connect the other meter probe to each connector at the other end of the cable. Check each connector and if any one fails to show continuity, the cable must be replaced.

7. Remove the motor cover on the support arm to expose the Dec motor. With the power off, check for continuity across the two electrical connections on the motor, in the same manner that you checked the RA motor. If the meter reads "Infinity," replace the motor. If the meter shows continuity, the motor is fine.

8. Check the continuity of each of the 8 connectors leading from the Dec motor to the cable connector on the support arm. Use the same technique that you used when checking the Dec cable. If any connector fails to show continuity, re-solder the connection.

9. Reconnect the Dec cable to the connector on the support arm and check the continuity for each of the 8 connectors running from the cable end to Dec motor. If the continuity check fails, re-solder the connectors. If the continuity check is OK, reconnect the Dec cable and turn on the telescope power. If the motor fails to run, the problem may be within the motherboard and may require replacing the board.

Tips & Warnings

• Remove the spotting scope before beginning repairs.

• Unplug the telescope from any power source before disassembling.

• Do not use acid-core solder on electrical connections

References

• "So You Want a Meade LX Telescope!: How to Select and Use the LX200 and Other High-End Models (Patrick Moore's Practical Astronomy Series)"; Lawrence Harris; 2010
• "How to Use a Computerized Telescope: Practical Amateur Astronomy Volume 1"; Michael A. Covington; 2002
• "Repairing the most common problems on the LX200 Dec/RA drive"; Bruce Johnston; undated
• "Dead LX200 - Things to Check"; Meade Advanced Product Users Group (MAPUG) & Amateur Astronomy Resource Website; undated