Tweco Troubleshooting Power Supply - Manual (Page 13)

13
When a phase is not missing the optoisolator, PHC2, output transistor is off or
open so voltage across CN7-1 & 2 is +15 VDC. When a phase is missing, the
opto turns on for the time that VACIN is lower than 2.5 V making the output
across CN7-1 & 2 into a string of low going pulses.
1
2
3
4
5
CN7
+15V
PCB5
PCB4
+
-
Pulse
Detector VACIN
1
2
4
3
PHC2
1
2
3
4
5
CN7
+12VDC
When L1 phase is missing, the voltage measured across CN7-1 & 2 will be less
than 15V, probably around 12 V.
Determining which PCB:
Disconnect CN7 from either PCB5 or PCB4. If 2-1 code still present after
restoring power then problem is in PCB5 or the CCM. If code went away then
look at PCB1 or PCB4. Also remember bad connections in harness connectors
can cause faults too.
PCB1
If 3 phase power of proper voltage is connected to the power supply and VACIN
is low or zero PCB1 or connections to it may be defective.
PCB4
If the voltage at CN7-1 & 2 is zero may indicate VACIN is not getting to PCB4
or PCB 4 is defective. Also possible there is a bad connection between PCB4 &
PCB5.
PCB5
If voltage across CN7-1 & 2 on PCB5 (same as CN7 on PCB4 unless bad
connection) +15V but LED2 on PCB 5 is illuminated then PCB5 is defective.
If LED2 is not illuminated, PCB5 should apply a low signal over the 34 ckt
ribbon cable from CN11-12 on PCB5 (common is TP0) to J36-12 (common TP1
on CCM I/O PCB) telling the CCM all 3 phases are present. If J36-12 is not low
then PCB5 is defective or the ribbon cable is open.
CCM
If J36-12 is low but code 2-1 is still flashing then CCM is defective.