HP 54645A User's And Service Manual page 220

Measure the power supply voltages at E1 through E6 on the system
2
board.
The test points are not marked on the system board; see the following figure
for the location of test points.
Make sure that the voltage measurements are within the following tolerances.
Table 7-12 Power Supply Voltage Tolerances
Supply Voltage
5.1 V
–5.25 V
15.75 V
15.75 V
Figure 7-4
Low Voltage Power Supply Voltage Test Points
(bottom side of oscilloscope)
Testing, Adjusting, and Troubleshooting
Tolerance
153 mV ( 4.947 V to 5.253 V)
158 mV (–5.092 V to –5.408 V)
+1.260 V, –787 mV ( 14.963 V to 17.010 V)
787 mV ( 14.963 V to 16.537V)
To adjust the power supply
7-31