Tweco Troubleshooting Power Supply - Manual (Page 22)

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Measure for 110 VAC on contactor coil. If present and contactor is not
energized then contactor is defective. If 110 VAC is not present, either PCB5 is
bad or no 110 VAC from T1 transformer.
PCB4 or PCB7
If unit has 2 or 3 inverters first determine which inverter is causing /READY
TO OPERATE to be false. With two or three inverters you can disconnect
ribbon cable from CN6 of one inverter at a time (other ones remain connected).
When 2-4 code goes away that is the inverter signaling the fault. Now you have to
determine if it is a PCB or the inverter causing the problem.
PCB4, Detector PCB
When configured for high voltage range (400, 460, 600V) a jumper in the
connector CN2 on the voltage change PCB (connects to CN4 on PCB4) of the top
inverter energizes relay RY2 on PCB4 (daughter board plugged into PCB3). The
normally open contact of RY2 becomes closed sending signal out from CN2-1 &
3 (PCB4) to CN4 on inverter PCB12. This tells the inverter that it is configured
for high range. Inverter then measures the incoming voltage to determine if it is
within expected value for high range. In low range RY2 is not energized and it’s
normally closed contact is across CN2-1 & 2 telling inverter it is configured for
208-230V. An open or intermittent connection of either the relay contact or the
harnesses (CN2 or CN4 of PCB4) will prevent the inverter from recognizing that
it is connected to the correct voltage so it will make /READY TO OPERATE
false.
PCB4 also supplies +12V on CN3-1 and another normally open contact of
RY2 applies ground to CN3-2 if RY2 is energized (high input voltage range).
This energizes relay RY2 on PCB7, the Relay board.
PCB7, Relay PCB
If unit has 2 or 3 inverters and either the second or third one has been
determined to cause the /READY TO OPERATE to be false then problem may be
PCB7 or harnesses connected to it.
As explained above if inverters are configured for high range (400, 460,
600V), relay RY2 (PCB7) is energized so it’s normally open contacts close the
connection between CN9-1 & 3 and CN10-1 & 3 sending signal to second and
third inverters if thy are present. An open or intermittent connection of either the
relay contact or the harnesses on PCB7 (CN2 to energize RY2 or CN9 or 10
sending signal to inverter) will prevent the inverter from recognizing that it is
connected to the correct voltage so it will make /READY TO OPERATE false
and set the 2-4 code.
If inverters are configured for low input voltage range then RY2 is not
energized so it’s normally closed contacts make connection between CN9-2 & 3
and CN10-2 & 3. Intermittent or open of the NC contacts or the wire harness on
CN9 or CN10 can cause /READY TO OPERATE to be false and set the 2-4 code.