Technical data

94 4000 X-Series Oscilloscopes Service Guide
4 Troubleshooting
To check the power supply DC output
This procedure checks the power supply DC output after
verifying the AC input is good and checking the power
switch operation.
1 Follow the instructions in “To prepare for internal
assembly troubleshooting” on page 83.
2 Connect the negative lead of the multimeter to a ground
point on the oscilloscope.
3 With the power cord disconnected:
a Disconnect the DC supply cable that is plugged into
J3700 of the system board.
4 Connect the power cord, and turn on the oscilloscope.
5 Verify there is +13V between pins 1 (- ) and 6 (+) of J3 on
the power supply.
If +13V is not present between pins 1 and 6 of J3 on the
power supply, replace the power supply.
If +13V is present between pins 1 and 6 of J3 on the
power supply, either the cable is wired incorrectly or the
power switch S101 is defective or has a solder short to
ground between one or some of its pins.
a Turn off the oscilloscope, and disconnect the power
cord.
b Replace the DC supply cable.
c Connect the power cord, and turn on the oscilloscope.
d Check again to see if the output of the power supply
turns ON and OFF as you actuate the power switch
S101.
If replacing the cable does not fix the problem, there is
something wrong with the power switch S101, and you
must replace the line filter assembly.