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3330B
3-99.
-25
VOLT POWER
SUPPLY.
AC
voltage
at
terminals
1
and
2
is
rectified
and
filtered
by
CRl
through
CR4
and
Cl
to provide
a
negative
operating voltage
for
the regulator
Q1
through Q3.
Diodes
CR5
and
CR6
pro-
duce
a positive operating voltage
for
the regulator.
The
comparator
amplifier
Q1
receives a
reference voltage
at
its
emitter derived
from
zener diode
CRl
2.
Variations
at
the
-25
volt
output
(terminal 6)
are
developed
across
the voltage
divider
of
R4
through
R6
and
applied
to the
base of
Ql.
Any
difference
between
the
base
and
emitter
voltage
of
Ql
is
amplified
and used
to
control
the
con-
duction of
the
series
pass regulator
Q2.
Conductions of
Q2
controls the
conduction of
the
series-pass transistor
Q3, which
establishes a
low-ripple
-25
volts
dc
output.
Variable
resistor
R5
allows
adjustment of the
regulator
output.
The
turn-on delay
circuit
consisting
of C4,
R7,
CR13,
Q4
and
K1
prevents the
-25
volt
output
from
appearing
at
terminal
6
for
approximately
three
seconds
after
initial
turn-on.
3-100.
-5
VOLT POWER
SUPPLY.
AC
voltage
at
terminals
14
and
15
is
rectified
and
filtered
by
CR7
through
CRIO
and C5
to
produce
a
negative
operating voltage
for
the regulator configuration
of
Q5
through
Q8.
Additional
negative operating voltage
is
obtained
from
the
—25
volt
power
supply through
R8
and RIO.
The comparator
ampli-
fier
Q7
receives
a
reference voltage
at
its
emitter derived
from
zener diode
CRll.
Variations
at
the
—5
volt
output
(terminal 16)
are
developed
across the
voltage
divider
of
Rll
and
R12
and
applied
through
RI4
to
the base
ofQ7.
Any
difference
between
the
base
and
emitter reference
voltage
of
Q7
is
amplified
and
used
to control the
conduc-
tion
of
the
series-
pass regulator
Q6.
Transistor
Q8
func-
tions as a
current
limiter
to
prevent the
output
current
from
exceeding
300 ma.
The
conduction of
Q6
controls
the
conduction
of the
series-pass
transistor
Q5, which
establishes
a
low-ripple
-5
volt
dc output
at
terminal
16.
Variable
resistor
Rll
allows
adjustment of
the
regulator
output.
3-101.
Pre-regulator
(A5A2)
3-102.
The
Pre-regulator controls the ac
power
dissipated
in
the
instrument
by
passing
only
enough power
to the
high
voltage
circuitry
to
meet
the
output load requirement.
The
Pre-regulator
consists
of
the
±V
power
supply
CRl
through
CR4,
a
relay
power
supply
CR6
through
CR9,
pre-regulator
drivers
Q2
and
Q4
through
Q7,
a pre-regulator
bridge
CRIO
through
CR13
and Ql, and
current
limiter
Q3.
3-103.
±V POWER
SUPPLY.
AC
voltage at terminals
1
and 12
is
rectified
by
CRl
through
CR4
to
provide un-
filtered
±V
operating
voltages.
Diode
CR5
provides
iso-
lation
of
a
+10
volt filtered
output.
Figure
3-6.
LADDER NETWORK
SIMPLIFIED
VERSION
3-12
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