E011—needle position signal error

(when the motor speed over 50rpm, “UP” signal keeps continuous 1s low frequency or high frequency, that means the frequency without change for continuous 1s)

Step of solution:
1) check the encoder socket and the main control encoder connect well or not
2) check the impedance of pin 1 / pin3 to pin2 of U1 of encoder board: around 0.7M, power supply with 80V isolation transformer, standby voltage: 1.2V. Test the both ends voltage D1: 0.5V
3) check the impedance of pin 3 to   pin 2 of Q1 of encoder board: around 0.8M, power supply with 80V isolation transformer, standby voltage: 5.1V. the impedance of foot 1 to pin 2 of Q1: around10K [note: when the encoder link to main control box, the impedance above is different] [ the voltage of U1 responsed to raster notch is around 0V]
4) check whether the pin 3/plug J1(4pins) of Q1 of encoder connect with the main control plugJ2(4pins)

5）Check the C30 two side impedance which on the main board: around 11K，the standby voltage:5.2V
6）Check the U2 (49pin) or U6 (16pin ) impedance to C4 negative terminal: around 3M, use 80Visolating transformer to supply power , the standby voltage:3.2