MKS 246C, Инструкция по эксплуатации

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Troubleshooting Chapter Five: Maintenance and Troubleshooting
72
Set Point Buffer and Flow Switching Circuit
If, with switches set for FLOW and ON, the maximum set point voltages is different from the
5 V reference TP4 and TP5, it may be possible to adjust the offset of U7A by using R25
(OFFSET ADJ) for 5.000 Volts out exactly. If not, suspect either U7 or possibly Q2.
With no REMOTE ON/OFF signal and either OFF or REMOTE selected on switch S2, the
voltage on the gate of Q2 should be approxi15 V, and the drain voltage should equal the
source voltage at around -0.08 ±.02 Volts. If not, determine which voltage is in error and then
why. With S2 in the ON state, Q2's gate should be at -15 Volts and drain should be at the set
point voltage (measure with high impedance probes). If not, Q2 may be the problem. Contact
MKS Instruments for assistance.