Teledyne 402REU - Hydrocarbon analyzer - Manual (Page 39)

Total Hydrocarbon Analyzer Maintenance and Troubleshooting
5-5 Teledyne Analytical Instruments
If performance is not adequate, then the analyzer must be
restandardized as described in Section 4-7: Calibration before being placed
back in service.
Whenever the flame guard and anode power supply printed circuit
board has been replaced, the flame guard circuit must be recalibrated (see
Section 5.3.1: Flame Guard Circuit Calibration) and the analyzer must be
restandardized.
If the instrument performs as outlined in this section, the problem is
not related to the measuring circuit electronics.
5.1.5 Collector Cable
Before reconnecting the collector cable, check the continuity of the
center wire of the cable with an ohmmeter by measuring between the
center pins at each plug on the lowest resistance scale of the meter. Flex
the cable while making this measurement to be sure that there is not an
intermittent open circuit. If there is, replace the cable. Do not attempt to
repair the cable, as special tooling is required to disassemble and reas-
semble the cable plugs.
5.2 Temperature Control Electronic Check
If the heating circuit fails, the output of the analyzer will tend to drift
with changes in ambient temperature. Such a failure will be more evident
in the low range. If the temperature environment surrounding the analyzer
is closely regulated, failure in this circuit might go unnoticed after the
initial failure. If the environment follows day and night temperature
changes, the analyzer will show a diurnal, bi-directional drift when oper-
ated on zero gas. The magnitude of the drift will be a function of the
temperature differential experienced by the analyzer. To check the circuit,
employ the following procedure:
Consult the 402R-EU schematic and assembly drawings, as well as
the temperature control PC board schematic and assembly drawings at the
rear of the manual for circuit details and component placement. See also
Figures 5-2 and 5-3 for the location of the Temperature Controller PC
Board.
1. An indicator light on the control panel cycles on and off with
the heating element; the light is on when the heater is on, and
vice versa. Failure of the light to come on at all when the cell
compartment is cold indicates a problem in the temperature
sensing or control circuitry or the wiring that interconnects the