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Troubleshooting and Service Teledyne API – Model T700 Dynamic Dilution Calibrator
264
9.4.15. TEMPERATURE PROBLEMS
Individual control loops are used to maintain the set point of the Photometer UV Lamp
(optional), and the Ozone Generator Lamp (optional). If any of these temperatures are
out of range or are poorly controlled, the T700 will perform poorly.
9.4.15.1. 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 9.1.3). This parameter will vary with
am
bient temperature, but at ~30
o
C (6-7 above room temperature) the signal should be
~1450 mV.
9.4.15.2. Photometer Sample Chamber Temperature
The temperature of the gas in the photometer sample chamber should read
approximately 5.0C higher than the box temperature.
9.4.15.3. 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 58oC set point is ~8.1k ohms.
06873B DCN6388