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Teledyne API T703 Calibrator Operation Manual General Troubleshooting & Repair
209
11.4.12. TEMPERATURE PROBLEMS
Individual control loops are used to maintain the set point of the UV lamp and ozone generator. If any of these
temperatures are out of range or are poorly controlled, the T703 will perform poorly.
11.4.12.1. Box / Chassis Temperature
The box temperature sensor is mounted to the motherboard and cannot be disconnected to check its resistance.
Rather check the BOX TEMP signal using the SIGNAL I/O function under the DIAG Menu (see Section 11.1.3).
This parame
ter will vary with ambient temperature, but at ~30
o
C (6-7 above room temperature) the signal
should be ~1450 mV.
11.4.12.2. Photometer Sample Chamber Temperature
The temperature of the gas in the photometer sample chamber should read approximately 5.0C higher than the
box temperature.
11.4.12.3. UV Lamp Temperature
There are three possible causes for the UV Lamp temperature to have failed.
The UV Lamp heater has failed. Check the resistance between pins 5 and 6 on the six-pin connector
adjacent to the UV Lamp on the Optical Bench.
It should be approximately 30 Ohms.
Assuming that the I
2
C bus is working and that there is no other failure with the Relay board, the FET
Driver on the Relay Board may have failed.
Using the PHOTO_LAMP HEATER parameter under the SIGNAL I/O function of the DIAG menu, as
described above, turn on and off the UV Lamp Heater (D15 on the relay board should illuminate as
the heater is turned on).
Check the DC voltage present between pin 1 and 2 on J13 of the Relay Board.
If the FET Driver has failed, there will be no change in the voltage across pins 1 and 2.
If the FET Driver Q2 checks out OK, the thermistor temperature sensor in the lamp assembly may have
failed.
Unplug the connector to the UV Lamp Heater/Thermistor PCB, and measure the resistance of the
thermistor between pins 5 and 6 of the 6-pin connector.
The resistance near the 58
o
C set point is ~8.1k ohms.
07223B DCN6378