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Troubleshooting & Repair Model GFC7001E Carbon Dioxide Analyzer
Teledyne Analytical Instruments 292
13.5.6.3. Opto Pickup Assembly
Operation of the opto pickup PCA (P/N 04088) can be verified with a voltmeter. Measure the AC and DC voltage
between digital ground on the relay board, or keyboard and TP2 and TP4 on the sync pickup PCA. For a
working board, with the GFC motor spinning, they should read 2.4 ±0.1 VAC and 2.5 ±0.15 VDC.
Further confirmation that the pickups and motor are operating properly can be obtained by measuring the
frequency at TP2 and TP4 using a frequency counter, a digital voltmeter with a frequency counter, or an
oscilloscope per Table 13-9.
Table 13-9: Opto Pickup Board Nominal Output Frequencies
Nominal Measured Frequency
AC Mains Freq. TP2 TP4
50 Hz 25 300
60 Hz 30 360
13.5.6.4. GFC Wheel Drive
If the D1 and D2 on the sync demodulator board are not flashing then:
1. Check for power to the motor by measuring between pins 1 and 3 on the connector feeding the motor.
For instruments configured for 120 or 220-240VAC there should be approximately 88 VAC for
instruments configured for 100VAC, it should be the voltage of the AC mains, approximately 100VAC.
2. Verify that the frequency select jumper, JP4, is properly set on the relay board.
For 50 Hz operation it should be installed.
For 60 Hz operation may either be missing or installed in a vertical orientation.
3. If there is power to the motor and the frequency select jumper is properly set then the motor is likely
bad.
See Section 13.6.2 for instructions on removing and replacing the GFC assembly that the motor is
bolted to.
13.5.6.5. IR Source
The IR source can be checked using the following procedure:
1. Disconnect the source and check its resistance when cold.
When new, the source should have a cold resistance of more than 1.5 Ohms but less than 3.5 Ohms.
If not, then the source is bad.
2. With the source disconnected, energize the analyzer and wait for it to start operating.
Measure the drive Voltage between pins 1 and 2 on the jack that the source is normally connected to;
it should be 11.5 ± 0.25 VDC.
If not, then there is a problem with either the wiring, the relay board, or the +12V power supply.
3. If the drive voltage is correct in step 2, then remove the source from the heat sink assembly (2 screws
on top) and connect to its mating connector.
Observe the light being emitted from the source.
It should be centered at the bottom of the U-shaped element.
If there is either no emission or a badly centered emission then the source is bad.