Table 3-1. Voltage Ranges And Fusing - HP 330 Service Information Manual

Input Section
Ac line voltage is supplied to the input section through the power cord. Functions of the input
section are:
• High Frequency Filtering.
• Fusing.
• On-Off Switching.
• Input Voltage Selection.
• Low Frequency Filtering.
t'Ugh Frequency Filtering
Line input voltage through the power cord is applied to a high-frequency line filter. This filter
traps high frequency noise from both entering or leaving the power supply. It enables the
output voltages to be virtually free from voltage spikes that may appear at the input. The
filtered output is sent to the fuse and power switch.
Fuse
For both line voltage ranges, the same size fuse protects the power supply. Voltage selection
and fuse size are shown in Table 3-1.
Table 3-1. Voltage Ranges and Fusing
Voltage Setting Tolerance Fuse Rating
120 Vac +10%, -25% 8AF 250 Volt
240 Vac
+4%, -19%
8AF 250 Volt
The fuse rating 8AF means an 8 arnpere fuse with a type F delay before blowing. In both cases,
the line frequency is 48-66 Hz.
Low Frequency Filtering
'Nhen the power switch is turned on, voltage is applied to the Low Frequency Filtering circuits.
These circuits trap low frequencies entering or leaving the power supply. They also reduce ripple
in the output voltages . . After filtering, the line voltage is sent to the Bridge Rectifier Section.
()n-Off Switching
This operator-controlled switch connects power to the Low Frequency Line Filter. Located on
the computer (or expander) front panel, it is mechanically connected to the power supply by a
switch extension. When turned to the ON position, a green LED on the front panel is lit. The
LED is connected to the voltage outputs and indicates that all power supplies are operating.
Input Voltage Selection
A voltage select switch is set to either the 120 Vac or 240 Vac position, depending on the line
voltage. Voltage selection changes the input voltage to the bridge rectifier to make the bridge
output the same for either line voltage.
Functional Description
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