HP 8340b User Manual

If
the
+20V
supply
fails,
only
the
+22V
supply
will
operate.
The
+20V
supply
is
energized
with
a
start-up current source
until
it
reaches
the
voltage
required
to
power
the
precision
+10V
reference.
The
+10V
reference serves
as
a
voltage
reference
for
the
+
20V
supply.
If
the
instrument
is
turned
off,
or
if
the
thermal
switch
temperature
threshold
is
exceeded,
the
+20V
supply
shuts
down.
The
reference
oscillator
supply
allows
the
10
MHz
reference
oscillator to be
turned
off
when
an
external
10
MHz
reference
is
used
The
5V
secondary
output
is
rectified
and regulated
to
generate
the
+5.2V
regulated
supply.
SUPPLY
FAILURE
MONITORING CIRCUITRY
HPUP
(high
power
up)
indicates whether
all
the
instrument
power
supply
voltages
are
operating.
If
a
supply
fails
or
is
low,
HPUP
is
low,
and
LIPS
(low
instrument preset)
is
low.
Pulling
LIPS
low
causes
the
instrument
microprocessor
to
reset,
protects
the
instrument
memory,
resets
the
A3
display
processor,
and
turns
on
all
front
panel LEDs.
LIPS
is
also
pulled
low
when
you
press
[INSTR
PRESET].
STANDBY MODE
When
line
power
is
connected,
and
the
front
panel
line
switch
is
in
the
STANDBY
position,
the
following
happens:
•
Power
is
supplied
to
the rectifiers
on
the
A19
and
ASS
assemblies.
•
The
+22V
regulator
(on
the
ASS
assembly)
is
powered
by
the
+20V rectifier
output
(+20V
UNPEG).
•
The
cathode
of
DS1
(front
panel standby
LED)
is
grounded,
lighting
the
LED.
•
A62K1
switches
(closes)
Into
standby
(fan
remains
off).
•
LSBY
(low
standby)
disables the
+20V
regulator.
WARNING
Although
the
+22V
regulator
is
the
only
operational
supply,
line
power
is
present,
the
rectifiers
are
fully
operational,
and
the
filter
capacitors
are
fully
charged.When
the line
switch
is
moved
to
on,
the
relay
is
discon¬
nected
from
ground,
providing
power
to
the
fan.
Simultaneously,
LSBY
goes
from
0
to
22V, allowing
the
+20V,
and
other
supplies,
to
operate.
HP 8340B/41B
Power
Supplies/Fan
Theory
of
Operation
I-5/1-6

HP 8340b Specifications

General

Brand	HP
Model	8340b
Category	Inverter
Language	English