Keysight N9000A - Power Supply Theory of Operation

164 Chapter 8
Power Supply/Midplane Troubleshooting
A5 Power Supply Description
Power Supply Theory of Operation
The A5 Power Supply assembly is serviced as an assembly only; no component
level repair is supported.
The A5 Power Supply assembly provides most all of the necessary DC voltages for
the CXA. If any of the power supplies are not within their operating voltages, the
instrument will not function properly.
The A5 Power Supply assembly is a switching supply that operates at a frequency
of ~120 kHz.
The A5 Power Supply assembly is an auto ranging supply, requiring no user
selection of the input voltage. The input AC voltage and frequency requirements
for the A5 Power Supply assembly are printed on the rear panel of the instruments
as well as on the power supply itself.
While there are no test points or status LEDs accessible for troubleshooting on the
A5 Power Supply assembly, there are both test points and status LEDs for all of the
different power supply voltages, as well as other power supply status lines, on the
A6 Midplane Board assembly. See the “A6 Midplane Description” on page 169
for detailed information on the location of each
Supply Voltages
The following voltage levels are produced by the A5 Power Supply assembly:
Control Inputs
There are a number of control inputs for the A5 Power Supply assembly. They are:
PS_ON PS_ON is a signal that when pulled low tells the A5 Power Supply
assembly to turn on all of its outputs. This signal comes from the A3 CPU board
assembly and is initiated by pressing the front panel power button.
DITHER DITHER is an AC coupled analog signal going to the supply that is
used to frequency modulate the power supply switching frequency for the purpose
of lowering any power supply related interference.
Voltag e
Level
Ground
Reference
A6 Midplane
Connector
Voltage
Level
Ground
Reference
A6 Midplane
Connector
+15V SB ACOM J101 +12V D DCOM J111
+5.1V SB DCOM J111/J112 +5.1V D DCOM J109/J110
+32V A ACOM J101 +3.35V D DCOM J107/J108
+15V A ACOM J103/J104 -15V A ACOM J105
+9V A ACOM J104 -7V A ACOM J105
+5.2V A ACOM J102 FAN POS FAN NEG J101
FAN NEG FAN POS J101