8. ELECTRICAL MECHANISM - Page 142

8. ELECTRICAL MECHANISM 

135

BAS-311G, BAS-326G

Problem  #21  Thread is not trimmed. 

Cause

Inspection/Remedy/Adjustment

Replacement if a malfunction

1.  Incorrect mechanism adjustment 
 

Adjust the thread trimming mechanism while 
refer to “7-17. Adjusting the thread trimming cam 
position”. 
(If it is clear that the thread trimming mechanism 
is not operating, carry out inspections 2. and 3. 
below.) 

2.  Poor connector contact 

Check that connector P1 (MAIN) is inserted into 
the PMD P.C. board. 

3.  Malfunction of thread trimming 

solenoid  

Disconnect connector P6 (SOL1) from the PMD 
P.C. board, and measure the resistance between 
pins 3-6 of the cord-side connector. 
OK if 6 

−

 8 

Ω

Thread trimming solenoid 

4. Malfunction of tension release 

solenoid/digital tension   

Disconnect connector P7 (SOL2) from the PMD 
P.C. board, and measure the resistance between 
pins 1-2 of the cord-side connector. 
OK if 6 

−

 8 

Ω

Tension release solenoid/ 
digital tension solenoid 

5.  Malfunction of PMD P.C. board   

1)  With  connector  P6  (SOL1)  connected  to  the 

PMD P.C. board, turn on the power and carry 
out sewing, and measure the voltage 
between pins 3-6 of connector P6 (SOL1). 
OK if voltage is output momentarily at the 
sewing end. 

2)  With connector P7 (SOL2) connected to the 

PMD P.C. board, turn on the power and carry 
out sewing, and measure the voltage 
between pins 1-2 of connector P7 (SOL2). 
OK if voltage is output momentarily at the 
sewing end. 

PMD P.C. board 

4889Q 

4890Q 

4891Q