Teledyne GFC-7000T - Trace CO2 Analyzer - manual - Manual (Page 261)

Troubleshooting Model GFC7000TA Carbon Dioxide Analyzer
Teledyne Analytical Instruments 243
10.5.6. Relay Board
The relay board PCA (04135) can be most easily checked by observing the condition of the its status
LEDs on the relay board, as described in Section 10.1.4.3, and the associated output when toggled on
and off through signal I/O function in the diagnostic menu, See Section 10.1.3.
1. If the front panel display responds to button presses and D1 on the relay board is not flashing,
then either the I 2 C connection between the motherboard and the relay board is bad, or the relay
board itself is bad.
2. If D1 on the relay board is flashing and the status indicator for the output in question (heater
power, valve drive, etc.) toggles properly using the signal I/O function, then the associated control
device on the relay board is bad. Several of the control devices are in sockets and can be easily
replaced. The table below lists the control device associated with a particular function:
Table 10-8: Relay Board Control Devices
FUNCTION
CONTROL
DEVICE
IN SOCKET
Wheel Heater K1 Yes
Bench Heater K2 Yes
Spare AC Control K3 Yes
IZS Valves U4 Yes
IR Source Drive U5 No
The IR source drive output can be verified by measuring the voltage at J16 with the IR source
disconnected. It should be 11.5± 0.5 VDC.
10.5.7. Sensor Assembly
10.5.7.1. Sync/Demodulator Assembly
To verify that the Sync/Demodulator Assembly is working follow the procedure below:
1. Verify that D1 and D2 are flashing (they flash at different rates, see Table 11-3).
 If not check the opto pickup assembly, Section 10.5.7.2 and the GFC wheel drive, Section
11.5.6.3.
 If the wheel drive and opto pickup are working properly then verify that there is 2.4 ±0.1 VAC
and 2.5 ±0.15 VDC between digital ground and TP 5 on the sync demod board. If not then
check the wiring between the sync/demod and opto pickup assembly (see interconnect
drawing 04216). If good then the sync/demod board is bad.
2. Verify that the IR source is operating, Section 10.5.7.4.
3. With the analyzer connected to zero air, measure between TP11 (measure) and analog ground,
and TP12 (reference) and analog ground.
 If they are similar to values recorded on the factory data sheet then there is likely a problem
with the wiring or the A/D converter.