Teledyne 4020 – Hydrocarbon analyzer (special version for automatic background gas switching) User Manual

Page 87

Total Hydrocarbon Analyzer

Maintenance

Teledyne

Analytical

Instruments

2. Then connect the DVM leads across tantalum capacitor C3. Note

the positive polarity is marked on the PCB. The Plus side
connects to ground. Measured voltage should be -15±1 volt.

If correct readings are not obtained at both points, power supply has

failed, and that 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: TAI recommends that spares for each of the printed

circuits be kept on hand so that service can be restored
immediately. The faulty circuit card can 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 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

125 VDC, check the voltage on either of the anode-igniter electrodes, as
follows:

1. Connect the negative voltmeter lead to ground and the positive

lead to either electrode. Be careful not to short the circuit by
touching both an electrode and the cell body simultaneously. The
reading obtained should be 125±10 VDC.

2. If no reading is obtained, disconnect the anode-igniter cable and

check for the voltage on pin “J4-1” of the connector located at
PC board part number B74671. If the proper voltage is still not
present, replace the flame guard and anode power supply PC
board. If it is, check the wiring in the anode-igniter cable plug. If
necessary, the circuit board can be replaced by first turning off
the power, then removing 4 screws holding the board.