Teledyne 4020 – Hydrocarbon analyzer (special version for automatic background gas switching) - Manual (Page 91)

Total Hydrocarbon Analyzer Maintenance
Teledyne Analytical Instruments 73
electrode cable. If steps 2 and 3 both check out properly,
reconnect the anode-igniter cable.
5. Check K1 and K2 relays operation as the analyzer is RE-
IGNITING. If the relays do not energize , remove the flame
guard power supply board and check the forward and backward
resistance of its transient suppression diode by measuring across
CR4 and CR5. The ohmmeter should indicate some resistance .
If the indication a short circuit, then the diode 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 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 defective.
IMPORTANT: If the circuit proves defective, the analyzer will have
to be recalibrated after the board is replaced.
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
performance. TAI recommends that the factory or an authorized
representative 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.,
5.5.1 Flame Guard and Anode Power Supply PCB
Schematic No. B-74672
Assembly Dwg. No.B-74671