Keysight Technologies Infiniium MSOV 084A, Service Manual

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68 Infiniium V-Series Oscilloscopes Service Guide
4
Troubleshooting
3
If there is a short, disconnect the power cable to the front panel and redo the
resistance measurement.
4
If the short is gone, replace the front panel assembly and verify that the
oscilloscope now powers on.
5
If there is still a short circuit, disconnect the two large connectors that provide
power to the motherboard (J1201 and J1202) from the backplane assembly as
shown below and redo the resistance measurements across the FET (Q1409) or
the bulk supply input pins on the backplane assembly.
I
6
If the short is gone, replace the motherboard assembly and confirm that the
unit powers on.
7
If there is still a short circuit, remove both acquisition boards and unplug them
from the backplane assembly.
8
Measure each assembly individually to see if there is a short between the +12 V
trace and ground (see following figure). You should see a resistance of about
2000 ohms between the +12 V trace and ground on a good acquisition
assembly. Make sure you make the measurement using a DVM with the red
lead plugged into the HI input and the black lead plugged into the LO or
COMMON input of the DVM. If there is a short between these two traces, the
reading you get will be very low (near 0 ohms). Replace either assembly if
needed.
Cable connection into backplane