Teledyne 402REU - Hydrocarbon analyzer - Manual (Page 43)

Total Hydrocarbon Analyzer Maintenance and Troubleshooting
5-9 Teledyne Analytical Instruments
5. Observe the K3 relay operation as the selector switch is moved
in and out of the IGNITE position (see Figure 5-3). If the relay
does not energize in the IGNITE position, remove it and check
it for an open coil (pins 13 and 14). The nominal resistance is
650
Ω.
If the coil checks OK, remove the flame guard power
supply board and check the forward and backward resistance of
its transient suppression diode by measuring pins 13 and 14 of
the relay socket. A multimeter should be set to the “diode test”
setting. The positive lead from the multimeter shall be
connected to socket number 13 on the relay socket and the
negative lead to socket 14. In this direction the multimeter
should indicate approx. 0.6 V and it should indicate an
overload when the lead connections are reversed. If these
readings are not obtained, then the diode (“D1” on the mother
PCB) must be replaced.
NOTE: If, after replacing a defective diode, the circuit still does not work
properly, the flame guard circuit components have been damaged,
and the flame guard PC board must be replaced.
6. If the preceding steps check out correctly, the flame guard
portion of the circuitry on the flame guard/anode power supply
PC board is either defective or needs recalibrating. Use the
following procedure to determine which problem exists:
IMPORTANT: If the circuit proves defective, the analyzer will have to be
restandardized (see Chapter 3: Stabilization Period) after the
board is replaced. (See section 5.1.4: Printed Circuit Board
Replacement.)
5.3.1 Flame Guard Circuit Calibration
1. With the selector switch in the high position, introduce span gas
into the sample path of the analyzer. Verify that all control
panel pressure readings are correct, and that the bypass flowrate
is 0.5 SCFH or greater.
2. Operate the selector switch in and out of the IGNITE position
until the presence of fuel is assured.
3. Observe the panel meter. If the meter reads up scale when the
selector switch is returned to the high position, ignition of the