Power Supply Adjustments; P O W E R Supply Switching Frequency - Agilent Technologies 4284A Service Manual

2-8. POWER SUPPLY ADJUSTMENTS

The following two part procedure adjusts the switching frequency and the output voltage of
the switching power supply.
2-8-1. POWER SUPPLY SWITCHING FREQUENCY ADJUSTMENT
This adjustment sets the switching frequency of the power supply.
EQUIPMENT:
Oscilloscope
10:1 Divider Oscilloscope Probe, 1 m n
PROCEDURE:
1. Make sure the HP 4284A is turned OFF.
2. Loosen the two screws holding the left hand side top shield plate (the shield
plate on which the WARNING message is printed), and remove it.
DANGEROUS VOLTAGES ARE PRESENT ON THE BOARD UNDER THE SHIELD
PLATE. DON'T TOUCH ANYPLACE EXCEPT WHERE INSTRUCTED TO.
3. Connect the 10:1 Probe to the Oscilloscope input.
4. Connect the probe's ground lead to A1TP12 (GND). T h e n connect the probe's
tip to A1TP11. Figure 2-4 shows the location of TP11 and TP12.
OSCILLOSCOPE
Figure 2-3. Power Supply Frequency Adjustment Setup
[WARNING
Ground to A1TP12
Tip to A1TP11
0 0 0 0 0 0
C O O 0 0
0 0 0
O
0 0 0
0 0 0
❑
0 0 0 0
L _ 1
2-10
HP 54111D
HP 10431A
10:1 Probe
HP 4284A
0
0
0
0
D
0 0 0 0 0 o
0 0 0 0 0 0 0
0 0 0
0 0 0
0
0 [ 0 0
0 0 0 1 = 1