Brooks Instrument 5866M - Manual (Page 26)

5-3
Troubleshooting
Table 5-1. Bench Troubleshooting.
Trouble Possible Cause Check/Corrective Action
Output stays at zero Volts regardless of com- Defective Sensor Replace sensor. Refer to Section 5-3 and Table 5-2.
mand and there is pressure on the controller.
Output stays at zero Volts regardless of Clogged Control Valve Check Pin 7 if the voltage is more than +11 V. Disassemble and repair the control valve.
command and there is no flow through the Refer to Sections 5-3 and 5-4.
controller.
-15 V applied to the valve override input. Check valve override input. Refer to Figure 2-2 for terminal assignments.
Defective printed circuit board. Replace printed circuit board. Refer to Sections 5-3 and 5-4.
Output signal stays at +14 V. regardless of Valve stuck open or leaky. Clean and/or adjust control valve. Refer to cleaning procedure and/or Section 5-5.
command and there is flow through the
controller.
+15 Vdc applied to the valve override input. Check the valve override terminal. Refer to Figure 2-2 for terminal assignments.
Defective printed circuit board Replace printed circuit board. Refer to Sections 5-3 and 5-4.
Command input floating. Connect command signal. Refer to Figures 2-1 and 2-2 for terminal assignments.
Output signal follows setpoint at higher Leaky control valve. Disassemble and repair valve. Refer to Sections 5-3 and 5-4.
commands but will not go to zero.
Excessive resistance in valve voltage return Reduce wiring resistance
line.
Output signal follows setpoint at lower Insufficient inlet pressure or pressure drop Adjust pressures, check calibration. Refer to Section 5-1.
commands but does not reach full scale.
Partially clogged valve. Disassemble and repair control valve. Refer to Sections 5-3 and 5-4.
Valve out of adjustment. Adjust valve. Refer to Section 5-5.
Valve guide spring failure. Controller oscillates (see below)
Controller oscillates. Pressure drop or inlet pressure excessive. Adjust pressures.
Oversized orifice Check orifice size. Refer to Section 5-6 and Table 5-4.
Valve out of adjustment. Adjust valve. Refer to Section 5-5.
P/I adjustment not correct. Adjust P/I potentiometers. Refer to Section 3-2.
Faulty pressure regulator. Check regulator output.
Defective printed circuit board Replace printed circuit board. Refer to Sections 5-3 and 5-4.
Table 5-2. Sensor Troubleshooting.
OHMMETER RESULT IF ELECTRICALLY
CONNECTION FUNCTIONAL
4 Sensor wires to body Open circuit on Ohmmeter.
(ground) If one of these is shorted,
(Pin 1 to 4 to body) an Ohmmeter reading will
be obtained.
Between the different Minimum 1 k Ohm
wires Maximum 4 k Ohm
Depending on sensor used
NOTE: Remove the sensor connector from the P.C. board
for this procedure.