4-2 Controller Troubleshooting
TP-5672 11/95
Power to the System
If there is a problem with the logic board, the first step is to
check the status panel. If no LEDs on the status panel
are illuminated and the liquid crystal display (LCD) is
blank, check the power to the system by performing the
following steps. See Figure 4-1 for the Power to the
System troubleshooting flowchart. See Appendix B
Figure B-4 for location of power supply board
components referred to in this section. See Appendix B
Figure B-6 for location and description of P2 ribbon cable
pins. See Appendix B Figure B-9 for location of main
logic board components referred to in this section.
1. Using a voltmeter, connect one test lead to
TB-AC1-NA. Connect the other test lead to
TB-AC1-NC. If the voltmeter does not read the
expected normal source voltage, check the normal
source and the contactor-to-assembly harness, P1.
2. If the normal source voltage is present, connect one
test lead to TB-AC1-NAS and the other test lead to
TB-AC1-NCS. If the voltmeter does not read
approximately 19 volts AC, the secondary normal
source voltage, check that the transformer is wired
correctly. If the transformer is wired correctly and
the voltmeter still does not read 19 volts AC,
disconnect transformer secondary wires and retest
transformer secondary voltage to determine if the
transformer or the logic board assembly is at fault.
3. If both the normal source voltage and the secondary
normal source voltage are present, connect one
test lead to TB-AC1-EA and the other test lead to
TB-AC1-EC. If the voltmeter does not read the
expected emergency source voltage, check the
emergency source and the contactor-to-assembly
harness, P1.
4. If the emergency source voltage is present, connect
one test lead to TB-AC1-EAS and the other test
lead to TB-AC1-ECS. If the voltmeter does not read
approximately 19 volts AC, the expected secondary
emergency source voltage, check that the
transformer is wired correctly. If the transformer is
wired correctly and the voltmeter still does not read
19 volts AC, disconnect transformer secondary
wires and retest transformer secondary voltage to
determine if the transformer or the logic board
assembly is at fault.
5. If the emergency source, normal source, and
transformers are all working properly, and the
battery back-up option is used, connect the positive
test lead to TB-DC1-29 and the negative test lead to
TB-DC1-34. If the voltmeter does not read between
12 and 30 volts DC, expected battery voltage, check
the battery-to-assembly wires and the battery.
6. Connect the positive test lead to TB-DC1-23, and
the negative test lead to TB-DC1-34. If the
voltmeter does not read between approximately 12
and 30 volts DC, check if an accessory is connected
to TB-DC1-23. If there is an accessory connected to
TB-DC1-23, disconnect it. If the voltmeter still does
not read between 12 and 30 volts DC, perform step
9.
NOTE
When taking a voltage or resistance measurement
at a ribbon cable pin, do not disconnect the ribbon
cable from the board. Use a needle point probe to
take the readings from the holes on the top side of
the ribbon cable connector.
7. Connect the positive test lead to P2-13, and the
negative test lead to TB-DC1-34. If the voltmeter
does not read approximately 10 volts DC, perform
step 9. See Appendix B Figure 6 for location of P2
ribbon cable pins.
8. Connect the positive test lead to TB-DC1-30 and
the negative test lead to TB-DC1-34. If the
voltmeter does not read approximately 10 volts DC,
perform step 9.
9. If each of the measurements taken in steps 6, 7, and
8 was correct, this step may be skipped.
a. Disconnect the main logic board ribbon cable
from P2, and recheck the voltages in steps 6, 7,
and 8. If the voltage readings in steps 6, 7, and 8
are now correct, the main logic board is
defective. Replace the logic board assembly.
b. If the logic board is equipped with a load shed
board, disconnect the load shed ribbon cable
from P10 on the main logic board, and recheck
the voltages in steps 6, 7, and 8. If the voltage
readings in steps 6, 7, and 8 are now correct,
replace the Load Shed board.
c. If the logic board is equipped with a remote
communications board, disconnect the remote
communications ribbon cable from P12 on the
main logic board, and recheck the voltages in
steps 6, 7, and 8. If the voltage readings in steps
6, 7, and 8 are now correct, replace the remote
communications board.
d. Disconnect the status panel ribbon cable from
P4, and recheck the voltages in steps 6, 7, and 8.
If the voltage readings in steps 6, 7, and 8 are
now correct, the status panel is defective.
Replace the logic board assembly.
e. If the voltages measured in steps 6, 7, and 8
were never correct, replace the power supply
board.
