Brother HE-800B Service Manual page 141

9. ELECTRIC MECHANISM
Error status #4 Work clamp does not return to home position during home position detection.
Probable causes
1. Incorrect depression
adjustment
2. Malfunction of treadle unit
3. Malfunction of foot switch and cord
(option)
4. Malfunction of foot switch adapter
harness (option)
position Adjust the position while referring to "7-21. Setting
method for standard depression strokes".
With the motor PCB connector P12 (PEDAL)
connected, turn on the power and measure the
voltage between pins 3-4 of the cord connector
(No. 3 +, No. 4 -).
OK if the voltage is approximately 2 V at neutral,
approximately 4 V when the foot switch is
depressed as far as it will go, and approximately
0.5 V when it is depressed backward.
2714B
(Check that the power is turned off.)
Disconnect the foot switch from the foot switch
adapter harness, and measure the voltage
between pins 5-6 and 7-8 of the foot switch
connector. (Check between pins 9-10 if using a
3-pedal foot switch.)
OK if the resistance is normally ∞ ohms but 0
ohms when depressed.
2956B
After checking the foot switch in step 3, connect
the foot switch adapter harness to the foot switch
and measure the voltage between pins 1-2 and
3-4 of connector P15 (PEDAL) of the main PCB.
(Check between pins 5-6 if using a 3-pedal foot
switch.)
(Touch the ohmmeter against the lead wires
without disconnecting the connector.)
OK if the resistance is normally ∞ ohms but 0
ohms when depressed.
2716B
Check/ repair/ adjust
HE-800B
Parts to be replaced
Foot switch
Foot switch
Foot switch
Foot switch cord
132