Teledyne 300E Instruction Manual page 204

TROUBLESHOOTING & REPAIR PROCEDURES
Sample Temperature
The Sample Temperature should closely track the Bench temperature. If it does
not, locate the sensor, which is located at the midpoint of the optical bench in a
brass fitting. Unplug the connector labeled "Sample", and measure the resistance
of the thermistor; at room temperature (25°C) it should be ~30K Ohms, at
operating temperature, 48°C, it should be ~ 12K Ohms
11.4.1.2. Bench Temperature
There are three possible failures that could cause the Bench temperature to be
incorrect.
1. The heater mounted to the bottom of the Absorption bench is electrically
shorted or open. Check the resistance of the two heater elements by
measuring between pin 2 and 4 (~76 Ohms), and pin 3 and 4 (~330 Ohms),
of the white five-pin connector just below the sample temperature sensor on
the Bench (pin 1 is the pointed end).
2. Assuming that the I
the Relay board, the solid-state relay (K2) on the Relay Board (see Figure
10-2) may have failed. Using the BENCH_HEATER parameter under the
Signal I/O function, as described above, turn on and off K2 (D3 on the relay
board should illuminate as the heater is turned on). Check the AC voltage
present between pin 2 and 4, for a 100 or 115 VAC model, and pins 3 and 4,
for a 220-240 VAC model.
WARNING: Hazardous Voltages are present during this test
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.
3. 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 48
11.4.1.3. 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.
204
2
C bus is working and that there is no other failure with
o
C setpoint it should have ~11K Ohms.
Model 300E Carbon Monoxide Analyzer
Instruction Manual
P/N 04288 Rev: A