E151—electromagnet loop overvoltage
Troubleshooting steps
1)To check the resistance of electromagnet by multimeter whether it is from1 to 9
2)to check Q13(trimming),Q14(pulling),Q18(foot lifting),Q19(backstich) resistance between foot1 and foot3(low pressure area) saperately whether it is 2K
3)To check diode of D13,D14 seperately (by multimeter ) whether it is 0.5V(a corss for negative pole checked by black pen of multimeter);To check diode of D24,D28 seperately (by multimeter ) whether it is 0.2V(a corss for negative pole checked by black pen of multimeter)
4)To check the C58’s resistance of mainboard which supplied by 80V isolation transformers whether it is around 3.2V(the foot4 toward foot3 of U21);To check the resistance between foot3 and foot4 of U39(low pressure area)which supplied by isolation transformers whether it is around 10.5K