iOptron HEM27 Manual

Ra stopper system inspection and replacement

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Jan. 2023

An HEM27 mount has a cable management system. To avoid cable damage, a mechanical stopper is implemented in RA

to prevent the mount rotating over 360 degrees.

Due to a large torque of the strain wave gear system, damage to the stopper might happen if

1. "Site and Time" incorrectly set.

2. Mount starts from incorrect zero position.

Please perform "MENU=>Zero Position=>Searching Zero Position" to establish Zero Position.

3. Manually slew the mount past meridian 20 degrees.

The following instruction discusses how to disassemble the HEM27 RA unit and to repair or replace the RA stoppers. The

tolls needed are a set of metric Allen wrench, a pair of tweezers, and a RA belt fixer.

1. Use a 2.5mm hex key to remove four (4) socket

screws that hold the RA frame cover, which has the

mount main board installed.

2. Separate 3 cables that connected to the main board.

Three cables are 12V for DEC board (4.5mm 2-wire

plug, J4), 12V_U for cable management system

(CMS) output (6mm 2-wire plug, J3) and iPoar (4

wire plug with center two twisted, J2).

iOptron Internal Use Only

HEM27 RA Stopper System Inspection and Replacement

3. Slightly pull RA and DEC control boards out from the

mount.

RA Board

DEC Board

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Page 1 3. Manually slew the mount past meridian 20 degrees. The following instruction discusses how to disassemble the HEM27 RA unit and to repair or replace the RA stoppers. The tolls needed are a set of metric Allen wrench, a pair of tweezers, and a RA belt fixer.
Page 2 Pull the motor out of 8. Separate the RA frame from the strain wave gear. the mount frame. You may use a screw driver to tap the black RA frame if it won’t be off easily. © Copyright iOptron 2023. All rights reserved.
Page 3 10. Use a 1.5mm hex key to release three (3) set screws wrapped onto the RA ring gear. on the Stopper Ring. Do not lose the set screws. Here is a close look at the deformed Stopper Ring. © Copyright iOptron 2023. All rights reserved.
Page 4 It can also be made by a piece of brass strip. as possible to the ring gear. Make sure that the pulley will inserted into the belt pocket instead of sitting on top of the belt or stay outside the belt © Copyright iOptron 2023. All rights reserved.
Page 5 LEFT/RIGHT arrow button you should see the RA ring gear moving. 21. There are small cut outs on the RA frame. The boards should be seated inside the cutouts to prevent it move when put the cover on. © Copyright iOptron 2023. All rights reserved.
Page 6 25. Plug in the HC cable and DC power. Power on the mount and test it. Align the RA motor wire over the DEC board. 23. Connect 3 wires to the main board © Copyright iOptron 2023. All rights reserved.