Keysight N6991A, Advanced Service Manual

Page: 36 / 83

1 Troubleshooting
36 Keysight RP7900 Series Advanced Service Guide
Figure 1-3 Hardware troubleshooting flow chart
START
Set the UUT voltage to 20 V
Measured 20 V
at UUT output?
•
Check the current accuracy with a load
or with the output terminal shorted.
•
If it is a performance issue, proceed to
re-calibrate and re-verify.
Any error
message?
NO YES
PFC red LED
indicator on?
Isolation red LED
indicator on or rail
voltage present?
Measure
the isolation circuit.
Is it 565 V?
Is the regulation rail
voltage indicator on?
NO
YES
YES
YES
•
PF: Verify the incoming power fault channel. If the verification fails,
check the biasing voltage to the PCA. The MOSFET may be shorted.
Swap the PFC module.
•
OT: Some components may be shorted or if there is a faulty sensor.
•
OC: The regulation MOSFET may be shorted. Swap the regulation
board.
•
Self-test error: Verify if there are any incompatible firmware in any
of the modules.
•
Check the PFC microcontroller LED.
•
Check the PFC self-test LED sequence.
•
Swap the PFC module.
YES
NO
•
Check the cable connecting to the PFC.
•
Check the PFC rail voltage and PG signal.
•
Swap the PFC module.
NO
•
Check that the biasing voltage (±23 ~ ±24 V) goes into the isolation
primary and secondary circuit.
•
Check that the microcontroller has been programmed with the
correct firmware.
•
The MOSFET on the isolation board may be shorted. Swap the
isolation board.
NO
•
Check the cable connecting to the isolation.
•
Check that the biasing voltage (±23 ~ ±24 V) goes into the
regulation board.
NO
Measure
the regulation output.
Is it 20 V?
YES
•
Check the ILmon signal on the regulation board.
•
The MOSFET on the regulation board may be shorted. Swap the
regulation board and the magnetic board.
NO
Verify that the
output board is producing
20 V at the bus bar.
YES
•
Check the Vmon, Imon, and Vloc signal on the output board.
•
Check if any IGBTS are shorted on the output board.
•
Swap the output board.
NO
Verify that the
control board Vmon and
Imon signals are good.
YES
•
Check that the biasing voltage (±24 V) goes into the control board.
•
Check the backplane connectors.
•
Check the FFC cable connecting to the control board.
•
Swap the control board.
NO
Swap the DPM
YES
END