TROUBLESHOOTING & REPAIR PROCEDURES
Model 400E Ozone Analyzer
Instruction Manual
256
P/N 04316 Rev: B
11.4.1.1.
Box or Sample Temperature
Box Temperature
The box temperature sensor is mounted to the Motherboard and can not 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 parameter
will vary with ambient temperature, but at ~30
o
C (6-7
°
above room temperature)
the signal should be ~1450 mV.
Sample Temperature
The Sample Temperature should read approximately 5.0
°
C higher than the box
temperature.
11.4.1.2.
UV Lamp Temperature
There are three possible causes for the UV Lamp temperature to have failed.
1.
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.
2.
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.
3.
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.