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Maintenance
Problem
Analyzer fails
to zero
Teledyne Analytical Instruments
Possible Cause
No flow or flow too
high to sample and
or reference inlets
Wrong gas used for
zero calibration or
wrong reference gas
No temperature
control at TCD
Failure of TCD
bridge power or
failure in a TCD
filament
2000RS
Solution
Check flows and make sure
they are adjusted properly:
50-200 ccm for zero
calibration gas, 50 ccm for
reference.
Verify what gases are
needed for calibration and
reference with factory.
Identify if thermistor is OK
by checking if temperature
reading is sensible. If
thermistor is OK, measure
resistance of heater in TCD
with a DVM. The value
should be in the range of
45 Ohms. If thermistor and
heater are OK, then main is
to be replaced.
To properly diagnose this
will require opening the
analyzer and removing the
TCD cover. Power across
TCD detector should be
measured between black
and red wires of TCD cable
and should measure about
4.3 vdc.
If power is OK, then
measure from black to
green wires, it should
measure about 2.15 vdc.
The same measurement
from black to white wires.
Consult factory.
102
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