Teledyne GFC7001T - page 269

Troubleshooting and ServiceTeledyne API – Model T300/T300M CO Analyzer
Teledyne Analytical Instruments 269
WARNING - ELECTRICAL SHOCK HAZARD
Hazardous Voltages are present during this test.
3. If the relay has failed there should be no change in the voltage across pins 2 and 4 or
3 and 4. Note: K2 is in a socket for easy replacement.
4. If K2 checks out OK, the thermistor temperature sensor located on the optical bench
near the front of the instrument could be at fault.
 Unplug the connector labeled “Bench”, and measure the resistance of the
thermistor.
 At room temperature it should have approximately 30K Ohms resistance;
near the 48oC set point it should have ~12K ohms.
12.4.1.3. GFC WHEEL TEMPERATURE
Like the bench heater above there are three possible causes for the GFC Wheel
temperature to have failed.
1. The wheel heater has failed.
 Check the resistance between pins 1 and 4 on the white five-pin connector
just below the sample temperature sensor on the bench (pin 1 is the pointed
end).
 It should be approximately 275 ohms.
2. Assuming that the I2C bus is working and that there is no other failure with the relay
board; the solid-state relay (K1) on the relay board may have failed.
 Using the WHEEL_HEATER parameter under the signal I/O function, as
described above, turn on and off K1 (D2 on the relay board should
illuminate as the heater is turned on).
 Check the AC voltage present between pin 1 and 4.
WARNING - ELECTRICAL SHOCK HAZARD
Hazardous Voltages are present during this test.
3. If the relay has failed there should be no change in the voltage across pins 1 and 4.
 K1 is socketed for easy replacement.
4. If K1 checks out OK, the thermistor temperature sensor located at the front of the
filter wheel assembly may have failed.
5. Unplug the connector labeled “Wheel”, and measure the resistance of the thermistor.
The resistance near the 68°C set point is ~5.7k ohms.
12.4.1.4. IR PHOTO-DETECTOR TEC TEMPERATURE
If the PHT DRIVE test parameter described in Table 11-3 is out of range there are four
possible causes of failure.