HP HP 54600B, User'S And Service Manual

Page: 132 / 183

5
Disconnect the display cable, then check the following signals on the
system board.
Table 4-18 Signals at U56
Signal Frequency Pulse width Voltage
U16 Pin 7 DE 19.72 kHz 38.0
µ
s 2.6 Vp-p
U16 Pin 24 Hsync 19.72 kHz 3.0
µ
s 5.0 Vp-p
U9 Pin 2 Vsync 60.00 Hz 253.5
µ
s 5.2 Vp-p
If the signals are good, replace the display assembly. If not, replace the
system board.
6
Disconnect the Low Voltage Power Supply ribbon cable from the
display board.
7
Measure the power supply voltages again (steps 1-3).
If the voltages are within the test limits, replace the display assembly. If not,
do the steps below.
a
Disconnect the power cord.
b
Disconnect the ribbon cable from the power supply.
c
Connect the dummy load to the power supply connector.
d
Connect the power cord, then measure the power supply voltages
again (see new tolerances below).
+
5.1 V (4.95 V to
+
5.25 V)
+
15.75 V (
+
15 V to
+
16.5 V)
−
15.75 V (
−
15 V to
−
16.5 V)
If the voltages are now within the test limits, replace the system
board. If not, replace the power supply.
Service
Troubleshooting the Oscilloscope
4–43