MAINTENANCE
HPR400XD Manual Gas Instruction Manual 5-55
3. Locate dipswitch S301 on the control board (PCB3) and move switch 5 to the ON position. The switch must be
returned to its original position before cutting.
4. Measure the open circuit voltage (OCV)
Attach the test leads of a DC volt meter to the NEG terminal and the WORK terminal on the I/O board. Turn ON the
power to start the chopper test. After the contactor (CON1) closes, read the OCV which should be about 360
VDC.
• If the OCV is 0, the chopper is probably faulty. Swap chopper 1 with chopper 2 for verification. If chopper 1 is
bad, the error code should change to 106. Replace chopper 1.
• If OCV is about 360 VDC, continue to step 5.
5. Swap current sensor 1 (CS1) with current sensor 2 (CS2). Move the sensor, but leave the power cable and the
control wiring in place.
• If the error remains on chopper 1, then replace the I/O PCB.
• If the error changes to chopper 2, replace CS1.
Chopper 2, 3, or 4 failure
1. Swap the current sensor for the chopper that failed with the current sensor for the next chopper in sequence.
• If the error changes to the next chopper in sequence, replace the current sensor for the chopper that failed.
• If the error remains on the original chopper continue to step 2.
2. Measure the OCV
• The chopper outputs are connected in parallel at the I/O board, and the choppers are tested in sequence (1, 3, 2,
and 4). This means that if you measure the OCV at the NEG and WORK terminals on a fully functional HPR400,
the voltage will be 0 until the contactor (CON1) closes. Chopper 1 will turn ON and you will measure 360 VDC.
Chopper 1 will turn OFF and the voltage will decrease to 0. Chopper 3 (1, 3, 2, and 4) will turn ON next, and the
voltage will increase to 360 VDC and then decrease to 0 when chopper 3 turns off. This sequence repeats until all
4 choppers are tested.
Example:
If you get error 075 or 107, you know chopper 3 failed the test. Because chopper 1 and chopper 2 passed the test,
you know the incoming power and the I/O board are OK. If you measure the OCV at the NEG terminal and the
WORK terminal on the I/O board, you will see the voltage cycle from 0 to 360, back to 0, and then to 360 again,
because chopper 1 and chopper 2 are OK. If you do not get the third reading of 360 VDC from chopper 3, that
means chopper 3 is faulty. You can swap chopper 3 with chopper 2 for verification. The error code will change to
chopper 2, if chopper 3 is faulty. If the error does not change, or you measure an OCV of about 360 VDC for
chopper 3, contact Hypertherm Technical Service at 800-643-9878
Note: Return switch 5 on S301 to the OFF position before returning to normal cutting operations.
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