Teledyne GFC-7001T - Trace CO Analyzer - Manual (Page 268)

Troubleshooting and ServiceTeledyne API – Model T300/T300M CO Analyzer
Teledyne Analytical Instruments 268
12.4. OTHER PERFORMANCE PROBLEMS
Dynamic problems (i.e. problems which only manifest themselves when the analyzer is
monitoring sample gas) can be the most difficult and time consuming to isolate and
resolve. The following provides an itemized list of the most common dynamic problems
with recommended troubleshooting checks and corrective actions.
12.4.1. TEMPERATURE PROBLEMS
Individual control loops are used to maintain the set point of the absorption bench, filter
wheel and IR photo-detector temperatures. If any of these temperatures are out of range
or are poorly controlled, the GFC7001T/GFC7001TM will perform poorly.
12.4.1.1. BOX OR SAMPLE TEMPERATURE
B OX T EMPERATURE
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 5.9.1). This parameter will vary with
ambient temperature, but at ~30°C (6-7° above room temperature) the signal should be
~1450 mV.
S AMPLE T EMPERATURE
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
12.4.1.2. 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 2 C bus is working and that there is no other failure with the relay
board, the solid-state relay (K2) on the relay board 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.