Teledyne 402REU - Hydrocarbon analyzer - Manual (Page 44)

Chapter 5 Model 402 R-EU
Teledyne Analytical Instruments 5-10
flame has occurred. If ignition failure is indicated (the meter
will read zero when the switch is in the high range), then refer
to Section 5.3: Ignition and/or Flame Guard Circuit Checks to
check the ignition circuit.
4. If ignition is verified, adjust the miniature potentiometer on the
flame guard anode power supply board until it is over 75% of
its travel clockwise (but not fully clockwise or counter-
clockwise), and repeat the ignition procedure. If the sensing
thermistor is intact (see step 2 under Section 5.3), and a fault
does not exist on the PC board, the flame guard circuit should
hold the flame-out indicator light in the off condition. If it does
not, replace the circuit board. If it does (or after a new board is
installed and the preceding steps completed), proceed with the
remaining steps of this section.
5. Turn the potentiometer slowly counter-clockwise until the
flame-out indicator light just comes on. Turn the potentiometer
gradually clockwise again (while repeating the ignition
procedure) until the light remains off. This adjusts the
sensitivity of the flame guard circuit. If properly adjusted, the
flame guard circuit should illuminate the flame-out indicator
light within 10-20 seconds after flame failure. This can be
easily tested by turning off the fuel and checking the light.
5.4 Sampling System
If the procedures outlined above do not correct the problem, the fault
must be related to the gas control systems. Plugged or faulty regulators,
plugged restrictors, or leaks within the system can cause erratic perfor-
mance. TET/AI recommends that the factory or an authorized representa-
tive be contacted before attempting any repairs to the sample or supporting
gas systems within the analyzer.
5.5 Printed Circuit Board Descriptions
The electronics circuitry of the analyzer is designed with the latest
integrated circuit technology. The individual circuits which are required to
process the incoming signal and condition it to provide the various outputs,
alarms, indicators, etc., are built upon separate plug-in printed circuit