Brother BES-1240BC Instruction Manual page 261

Symptom
The needle stop position error oc-
curs.
The needle bar case lock error oc-
curs.
• Is the main shaft brake solenoid operating?
If not, refer to the block diagram showing the cable connections and
check to see if the connections from the brake solenoid to the power
PCB and from connector P27 of the power PCB to connector P1 of the
main PCB are proper.
• Check the resistance value of the main shaft brake solenoid at the
connector section of the solenoid. The normal resistance value is
approximately 50 .
If it is not normal, replace the solenoid with a new one. In this case, the
power PCB in the control box may also be faulty. Replace it with a new
one if it does not operate properly even after a new solenoid is installed.
• Are there any problems with the main shaft mechanism? (i.e., The
screw of the main shaft pulley is loose.)
• Is the INDEX motor rotating?
If not, refer to the block diagram showing the cable connections and
check to see if connection from the INDEX motor to the main PCB is
proper.
Check the resistance values of pins 1 and 2 and pins 3 and 4 at the
connector section of the INDEX motor. The normal resistance value is
approximately 4.4 .
If it is not normal, replace the INDEX motor with a new one. Also
replace the main PCB with a new one.
• Manually turn the color change pulley.
If it is abnormally heavy, adjust the color change mechanism and
the needle cap case.
• Start the machine after invalidating its initial setting and operate the
head solenoid in solenoid test mode.
If a certain head and the heads following it do not operate, refer to
the block diagram showing the cable connections and check to see if
connection of the head communication sign is proper.
• Only head 1 does not operate.
Check the communication line to head 1 and connection of the power
harness for head 1.
• Do the rotary switch settings of each head PCB correspond with the
numbers of each head?
If not, set them according to the head numbers.
• Start the machine after invalidating its initial setting and enter the CASE
test mode. Do figures on the panel change when the color change pulley
is manually turned?
If not, check to see if connection from the needle bar position sensor
to connector P7 of the head PCB (1) is proper.
• Replace the needle bar position sensor (potentiometer) with a new one.
• Replace the head PCB 1 with a new one.
BES-940BC • BES-1240BC
Chapter 12 Trouble Shooting
Measures
259