Troubleshooting - Brother LH4-B800E Service Manual

6-8. Troubleshooting

Code
1. Turn off emergency stop switch.
2. Check if connector P10 on the main circuit board is securely inserted and if any harness is
broken or short-circuited.
3. With the power turned off, separate connectors P10, and check if continuity between the
following pairs of pins 1 to 3 in the connector on the harness is as follows:
- When emergency stop switch is activated, between pins 1 and 2 is opened, and between
E-00
pins 2 and 3 is short-circuited.
- When emergency stop switch is not activated, between pins 1 and 2 is short-circuited, and
between pins 2 and 3 is opened.
* If the result of continuity test is not acceptable in either case, replace the emergency stop switch.
4. If there is still an error even after replacing the emergency stop switch, replace the main circuit
board.
1. Check if connector P10 on the main circuit board is securely inserted and if any harness is
broken or short-circuited.
2. Check the operation of the thread breakage sensor monitor lamp.
- When the dog is nearby, the monitor lamp lights.
E-01 - When the dog moves away, the monitor lamp switches off.
* If the result of continuity test is not acceptable in either case, replace the thread breakage
detection sensor.
3. If there is still an error even after replacing the thread breakage detection sensor, replace the
main circuit board.
1. Turn the pulley manually to set the needle to its highest position.
2. Check if connector P3 on the main circuit board is securely inserted and if any harness is
E-02 broken or short-circuited.
3. Replace the synchronizer.
4. If there is still an error even after replacing the synchronizer, replace the main circuit board.
1. Check if connector P11 on the main circuit board is securely inserted and if any harness is
broken or short-circuited.
2. Check the operation of the zigzag home position sensor monitor lamp.
- When the dog is nearby, the monitor lamp lights.
E-05 - When the dog moves away, the monitor lamp switches off.
* If the result of continuity test is not acceptable in either case, replace the zigzag home position
sensor.
3. If there is still an error even after replacing the zigzag home position sensor, replace the main
circuit board.
1. Check if connector P11 on the main circuit board is securely inserted and if any harness is
broken or short-circuited.
2. Check the operation of the feed home position sensor monitor lamp.
- When the dog is nearby, the monitor lamp lights.
E-06 - When the dog moves away, the monitor lamp switches off.
* If the result of continuity test is not acceptable in either case, replace the feed home position
sensor.
3. If there is still an error even after replacing the feed home position sensor, replace the main
circuit board.
Countermeasure
LH4-B800E
6. ELECTRIC MECHANISM
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