Teledyne 402REU - Hydrocarbon analyzer - Manual (Page 37)

Total Hydrocarbon Analyzer Maintenance and Troubleshooting
5-3 Teledyne Analytical Instruments
5.1.1 Loss of Zero Control
If the zero cannot be controlled as directed above, a failure has oc-
curred in either the differential power supply or the electrometer-amplifier.
Use the following procedure to isolate the fault:
With a digital voltmeter (DVM) set to read 15 VDC, check the posi-
tive and negative 15 V output of the power supply as follows:
(See schematic and assembly drawings for the differential power
supply PC board. Additional information can be found in the printed
circuit board description section at the end of this chapter.)
1. Connect the negative voltmeter lead to the common (pin 2) and
the positive lead to pin 15 of connector J5. The measured
voltage should be 15±1 volt. See Figure 5-1.
2. Then connect the positive DVM lead to pin 1 of connector J5.
Measured voltage should be -15±1 volt.
If correct readings are not obtained at both points, the differential
power supply has failed, and the printed circuit card must be replaced. If
correct readings are noted, the electrometer-amplifier has failed, and that
printed circuit card must be replaced.
NOTE: TET/AI recommends that spares for each of the printed circuits be
kept on hand so that service can be restored immediately. The
faulty circuit card should be returned to the factory for repair.
Unless personnel knowledgeable in electronics are available, do not
tamper with the circuits.
5.1.2 Anode Voltage Check
If the output can be adjusted by the zero control (the above section,
step 2), the cell anode voltage should be verified as follows:
WARNING These procedures should be caried out only by suitably
trained personnel familiar with high voltage circuit
boards. The anode-igniter unit and associate circuitry
involve dangerously high voltages.
Refer to the cell wiring diagram. Using a voltmeter set to measure 299
VDC, check the voltage on terminal four on the terminal strip TS6 on the
(mother) PCB, as follows:
1. Connect the negative voltmeter lead to ground and the positive
lead to TS6 terminal 4. Be careful not to short the circuit by
touching both an electrode and the cell body simultaneously.
The reading obtained should be 250±22 VDC.