Teledyne 402REU - Hydrocarbon analyzer - Manual (Page 41)

Total Hydrocarbon Analyzer Maintenance and Troubleshooting
5-7 Teledyne Analytical Instruments
wire and the remaining undisturbed terminal. See Figure 5-3.
Resistance of the thermistor varies with its surrounding
temperature. A reading of between 10K
Ω
and 20K
Ω
at around
25 °C may be measured. (Under very cold conditions, the
resistance could be as high as 50K
Ω
; under hot conditions, just
a few thousand ohms.) If the thermistor measures anywhere in
this range, it is most likely OK. Otherwise, if the circuit is open,
check the wires leading to the thermistor.
4. Check the heating element by measuring its resistance.
Disconnect one of the heater wires from either terminal 3 or
terminal 4 of TS-2 on the motherboard which is shown in
Figure 5-3, and check the resistance between that wire and the
remaining undisturbed terminal. If a reading of 288
Ω
±10% is
found, then the heating element is most likely OK. If an open
circuit is found, check the heater wires and a possible connector
between the heater and TS-2. If no problems are found, and the
heater circuit is open, then replace the heater element.
Figure 5-3: Motherboard