MKS 250E - Table 11: Troubleshooting Chart

Chapter Five: Maintenance and Troubleshooting Troubleshootin
g
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Troubleshooting Chart
Symptom Checks and Probable Causes
Error Meter shows oscillation or noise
(Optional DVM reading is noisy)
a. Check to see if input gas pressure is steady.
b. Check that pressure transducer has a steady
output (vibration isolation may be required).
c. Check that diffusion pump is not choking.
Refer to
System Design
, page 14.
d. Readjust PHASE and/or GAIN controls.
Refer to
How To Tune-Up the Controller
,
page 30.
Error Meter shows steady error greater than
±0.25%
(Optional DVM reading does not agree with set
point)
a. Increase GAIN setting. Refer to
How To
Tune-Up the Controller,
page 30.
b. If reading is higher than set point, try
lowering BIAS.
c. If reading is lower than set point, check that
incoming gas supply is adequate.
d. Check valve operation in Manual mode.
e. If mode control is in EXT, remote controller
may be overriding. Remove Interface
connector to verify.
f. Check that Normal/Reverse switch (inside)
is set correctly (usually NORMAL).
g. Check that set point input is correct.
Error Meter shows error less than 0.25% but
pressure is not correct
a. Check that Power is ON.
b. Check that pressure transducer signal is
proportional to pressure.
c. Trouble in Amplifier or Set Point Amplifier.
Table 11: Troubleshooting Chart