Brother RH-981A Service Manual page 131

7. SOFTWARE
Code
1. Turn the pulley manually to set the needle to its highest position. ("UP" will appear on the display.)
2. Check if connector P2 (SYNCHRO) on the control circuit board is securely inserted and if any
harness is broken or short-circuited.
3. With connector P2(SYNCHRO) inserted into the PCB in the input check mode, check the voltage
across pins 4 and 5 from the harness as follows:
E-10
• Considering pin 5 as 0V (standard), measure the voltage of pin 4 while turning the pulley
manually. It is normal if the voltage is 0V with the needle at its highest position, and 4 – 5V
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everywhere but that position.
E-76
* If the result is not acceptable, check how the magnet of the pulley is attached, and if it is correct,
replace the synchronizer.
* Even if the result is acceptable, the harness may be broken or short-circuited. It may appear when
oscillation occurs.
4. When there is no problem with the above, replace the control circuit board.
1. Position knife correctly.
2. Make sure that knife driving valve is supplied with air and wiring is correct.
3. Make sure that knife ON sensor and neighboring parts are attached correctly.
E-12
4. Check if connector P3 (HEAD) of the control circuit board is inserted and if any harness is broken or
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short-circuited.
5. Replace knife ON sensor and its harness.
6. Replace the control circuit board with a new one.
1. Check if cylinder is in place. (Check if air is supplied normally, position is correct, nothing caught on
the cylinder, and so on.)
E-15
2. Check if connector P8 (EXINA) on the control circuit board is securely inserted and if any harness is
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broken or short-circuited.
E-75
3. Replace lower thread trimming OFF sensor and its harness.
4. Replace the control circuit board with a new one.
1. Check if connector P20 (PER) on the control circuit board is securely inserted and if any harness is
broken or short-circuited.
2. Check if connector P2 (PER) on the power supply circuit board is securely inserted and if any
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harness is broken or short-circuited.
3. Replace the power supply circuit board with a new one.
4. Replace the control circuit board with a new one.
1. Check if ROM chips of the control circuit board or panel circuit board are correctly inserted.
(Check position, orientation, lead clinching, etc.)
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2. Replace the panel circuit board with a new one.
3. Replace the control circuit board with a new one.
1. Check if ROM chips of the control circuit board or panel circuit board are correctly inserted.
(Check position, orientation, lead clinching, etc.)
2. Check if connector P2 (MAIN) on the panel circuit board is securely inserted and if any harness is
broken or short-circuited.
E-28
3. Check if connector P18 (PANEL) on the control circuit board is securely inserted and if any harness
is broken or short-circuited.
4. Replace the panel circuit board with a new one.
5. Replace the control circuit board with a new one.
1. Make sure that ROM chips of the control circuit board are correctly inserted. (Check position,
orientation, lead clinching, etc.)
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2. Replace the control circuit board with a new one.
1. Check if air is supplied to valve unit of the indexer or wiring is correct.
2. If the cloth feed bar of the indexer works correctly, skip to step 5 below. (This is because the place to
be checked is different if the failure is with the sensor or driving system.)
3. Check if the valve harness of the indexer is connected to the indexer relay cord and connector P21
(EXOUT) on the control circuit board.
* Check if there is no pin that is out of place in either of indexer relay connector and P21.
4. Check if feed plate works in output check.
E-38 5. Of connectors relayed to head harness, check if the harness for the right driving sensor (cylinder
E-68 sensor) is correctly attached to the connector for the θ-axis home position sensor. (The brown
harness should be attached to pin 4, the black one to pin 9, and the blue one to pin 14. Refer to the
instruction manual.)
* Check if there is no harness in the control box that is broken or short-circuited.
6. Check if connector P9 (EXINB) on the control circuit board is securely inserted and if any harness is
broken or short-circuited.
7. Replace the right driving sensor and its harness.
8. Replace the control circuit board with a new one.
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Countermeasure
RH-981A