Power Supply Switching Frequency Adjustment; Power Supply Adjustm Ents - Agilent Technologies 4284A Service Manual

2-8. POWER SUPPLY ADJUSTME NTS
The following two part procedu re adjusts the switching frequency and the output voltage of
the switching power supply.
2-8- 1 . POWER SUPPLY SWITCHING FREQUENCY ADJUSTME NT
This adjustment sets the switching frequency of the power supply.
EQU I PMENT:
Oscil loscope
1 0: 1 Divider Oscilloscope Probe, 1 Mn
PROCEDURE:
1 . M ake sure the H P 4284A is turned OFF.
2 . Loosen the two screws holding the left hand side top sh ield 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 1 0: 1 Probe to the Oscilloscope input.
4. Connect the probe's g round lead to AHP 1 2 (GN D
tip to AHP1 1 . Figure 2-4 shows the location of TP1 1 and TP1 2 .
OSCI LLOSCOPE
D I
0
Figure 2-3 . Power Supply Frequency Adjustment Setup
Ground to A1TP12
Tip to A1TP11
000000
000 00
000
000
C9
ODD
0
2-1 0
H P 541 1 1 0
H P 1 0431 A
)
. Then connect the probe's
10:1 Probe
0 �
00000
4284A
HP
ODD'
O M
DODO
o
0
0 0 000
o
o
0
0
.
0
0