130 Maintenance and Service 083730300A DCN8101
5.7.14.6 RELAY BOARD
The relay board PCA (P/N 04135) can be most easily checked by observing the condition
of the its status LEDs on the relay board, as described in Section 5.7.8, and the associated
output when toggled on and off through signal I/O function in the diagnostic menu, see
Section 5.7.4.
1. If the front panel display responds to button presses and D1 on the relay board is
NOT flashing then either the wiring between the touchscreen and the relay board is
bad, or the relay board 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 5-11. Relay Board Control Devices
FUNCTION
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.
5.7.14.7 SYNC/DEMODULATOR ASSEMBLY
To verify that the Sync/Demodulator Assembly is working, follow the procedure below:
1. Verify that D1 and D2 are flashing.
• If not, check the opto pickup assembly, Section 5.7.14.8 and the GFC Wheel
drive, Section 5.7.14.9.
• 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, P/N 04216). If good then the
sync/demod board is bad.
2. Verify that the IR source is operating, Section 5.7.14.10.
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.
• If they are not then either the sync demodulator board or the IR-photodetector are
bad. See Section 5.7.12.5 for problems with the IR-photodetector TEC drive.
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