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HP 400D Operating And Service Manual

HP 400D
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Section
IV
Paragraphs
4-12
to
4-16
4-12.
During
the
negative-going
half
cycle
of
the
plate
voltage
of
V5,
rectifier
CR2
conducts
electrons
back
to
both
C32
and
C33
from
the
plate
of
V5.
That
portion
of
electrons
going
back
to
C32
flows
through
the
meter
on
the
way
(in
the
same
direction
that
the
electrons
flowed
in
the
first,
positive,
half
cycle).
At
this
point
in
the
cycle,
both
C32
and
C33
are
discharged.
The
pulsating
current
through
the
meter
is
smoothed
by
C34
to
prevent
meter
pointer
vibration
when
measuring
low-frequency
signals.
The
current
is
proportional
to
the
arithmetic
average
value
of
the
waveform
ampli-
tude
of
the
signal.
Meter
calibration
in
rms
volts
is
based
on
the
mathematical
ratio
between
the
average
and
rms
values
of
true
sine
wave
current.
4-13.
In
addition,
the
bridge
serves
as
a
segment
of
a
voltage
divider
(in
series
with
L11
and
R108)
connected
across
the
output
of
the
amplifier.
The
negative
feedback
voltage
fed
to
the
input
of
the
amplifier
is
obtained
across
L11
and
R108,
The
alternating
charge
and
discharge
of
C32
and
C33
produce
at
their
junction
with
L11
an
al-
ternating
current
of
the
same
phase
and
waveform
as
that
at
the
plate
of
V5.
This
phase
is
negative
with
respect
to
the
input
signal
applied
to
the
first
stage
of
the
amplifier
(V2),
and
drives
the
negative
feedback
network.
4-14.
POWER
SUPPLY.
4-15,
The
power
supply
consists
of
tubes
V6
through
V9
and
the
associated
circuits,
as
shown
in
the
complete
T.O.
33A1-12-349-1
schematic
diagram,
figure
5-10.
The
power
supply
furnishes
regulated
+250V
d-c
voltage
for
the
grid
and
plate
bias
circuits
of
tubes
V1
through
V5,
unregulated
12.6V
d-c
voltage
for
the
heater
supply
of
tubes
V1
through
V4,
and
6.3V
a-c
voltage
for
the
heater
supply
of
tubes
V5
through
V8.
The
power
supply
is
designed
to
operate
from
either
a
115-volt
(410%)
or
a
230-volt
(£10%)
a-c
power
source
of
50
to
1000
cps.
The
primary
winding
of
power
transformer
T1
is
arranged
in
two
sections,
which
can
be
strapped
either
in
parallel
or
in
series,
to
permit
operation
on
115V
or
230V,
respectively.
4-16.
The
output
of
rectifier
V6
is
applied
to
the
voltage
regulator
circuit
consisting
of
V7
through
V9
which
supplies
a
constant,
+250
volts
de
to
the
stabilized
ampli-
fier
circuit
of
the
voltmeter.
Tube
V7
is
the
series
regulator
tube,
and
V9
provides
a
fixed
reference
voltage
drop,
with
which
the
output
voltage
is
compared
in
ampli-
fier
V8B.
V8A
is
a
cathode
follower
which
couples
the
reference
voltage
from
V9
to
V8B
without
loading
V9.
The
regulated
output
voltage
is
applied
to
the
control
grid
of
V8B,
while
the
reference
voltage
is
applied
to
its
cathode.
The
difference
between
the
control
grid
and
cathode
voltages
controls
the
operating
point
of
V8B
and
thus
its
plate
voltage,
which
in
turn
supplies
the
grid
voltage
for
regulator
V7.
Any
change
in
the
regu-
lated
output
of
V7
produces
a
correcting
change
in
the
grid
bias
of
V7
through
the
action
of
V8B,
thus
maintaining
an
essentially
constant
output
voltage
despite
changes
in
line
voltage
or
load
on
the
supply.
The
gain
of
V8B
is
high
enough
to
keep
the
output
at
the
V7
cathode
regulated
LEGEND:
DIRECTION
OF
CURRENT
FLOW
POSITIVE
HALF
OF
CYCLE
———»
NEGATIVE
HALF
OF
CYCLE
———=
posimve
HALF
oF
crete
/_\
NEGATIVE
HALF
OF
cycLE
/
\
Figure
4-2.
Simplified
Schematic
of
Meter
Bridge
Circuit
4-2
00102-2

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HP 400D Specifications

General IconGeneral
BrandHP
Model400D
CategoryMeasuring Instruments
LanguageEnglish

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