Tektronix 543B Instruction Manual page 14

Circuit
Description
—
Type
543B/RM543B
<63*
"e
series-string
filomenls
hove reoched
*9 •e-^serc-ure.
When
K601
is
ocfivolcd
by K600.
j
r-
""'SC*: K6C1-3
shift
the
series-string
filoments to the
•ec. s -*3
c.-e,- of rne i-lOO-voil supply.
*s
-e'S'e-ce vol'oge source
is
the rcgulotcd output
of
•*f
—
15C-vclr
supply.
V664
is
the
error omplifier,
or>d
•
6
"A
s
•-*
series
regulotor
tube.
The
error-feedbock
:
• 8
•'rough R650 ond
R651, the
junction
of
which
is
-t
•'e grid
of
V664. The fop
end
of
R650
is
ro rhe rcgulotcd +lW3-voit output
and
the
lower
*•;
;•
R651
is
connected
to the
output of the reguloted
—
'53--0' supply
to obtoif?
reference voltage.
With
norirol
-i
.o'ages end loods, the voltage
of the junction of
R650
S651
is
about
—
1.7
volts
with
reference to
ground;
s
5
•'5
operaring
bios of V664.
-
—
e -ood current,
output volfoge, or the input vollogc
:-=*ces
[including
changes due
to ripplej, the
output
of the
'vC. a-ed
-100-volt supply
starts
to
change
olso,
but
ony
:-:-ge oppears
across
R650
and
R651
ond
is
applied
to
the
a- a of
V664
os a
change
in
operating
bios.
Assuming
thol
--e
ou-put of the regulated
—
iOO-volt
supply
fries
to
de-
:'c-oso,
'he
reduced
voltage at the top
end
of
R650
permits
•e
'.'o.iage
at
the junction of R650
and
R651
to
go more
'cgotive than the
normal
—
1.7-volt level
at that point,
"ne
increase
in
negative
bios
on
the grid
of
V664
reduces
•-e
flow
of
plate current
through V664,
the
voltoge drop
across plate-load
resistor
R663
decreases,
and
the
plate
-O'tage
of
V664 and
the grid bios of
V677A go more
posi-
rlv9.
As
the grid of
V677A
goes
more
positive, the resistance
tnot
V677A
offers to the
flow
of current
is
decreased ond
the output voltage
rises,
compensating
for
the
drop
in
output
voltage which
initiated reguloting ocHon.
Of
course, the
regulator
circuit
con never completely compensate
for
a
change
in
output voltage,
for there
must be
on
error input
for the
circuit to
operate, but
erny error
in
output
is
reduced
by
0 factor equal
to the
loop gain
of the regulatw-
circuit.
The
screen grid of
V664
is
used
as o
signal grid
for in-
lecfing
a
sample
of
any
ripple or tronsicnf voltoge
present
in
the unregulated side of the
—
100-voit supply
irjfo
the
regulator
circuit.
The regulator
circuit
thereby
^comes
o
dynamic
filter
for ripple reduction.
The
ripple signal
is
applied
to the screen of
V664, omplified and
inverted
in
phase by V664,
then applied
to the grid
of V677A. By the
time the amplified
end
inverted ripple gets to the grid of
V677A,
it
is
of
proper omplifudo and phose
to
concel out
the ripple
appearing
at
the plate of
V677A.
Unregulated
+
325-Volt Supply. The
unregulated
-h325-
volf
supply voltage source
differs
somewhot
from
the
voltage
source
for
the
-150- and
4-100-voll
supplies.
A
center-
topped
secondary on
T601
(pins 5, 7, 10,
and
14)
and
silicon
diodes
D702 and D732
form a center-topped bridge
rectifier
circuit
with
the negative
side
connected
to the positive un-
reguloted
side
of the
voltage source
for
the
+
100-voit
supply.
The unrcgulotod
-(-325-voli
output
is
taken from the
tronsformer centcr-top
{pins
7
ond
10) cor>oecfion.
The unregulated
output
of
the voltoge source
lor the
-t-lOO-volt
supply
is
approximately 4-180
volts.
The
ur^reg-
uloted output
of
the center-topped bridge
circuit
is
opprox-
imotely 4-290
volts;
this
added
to
the
onreguioted
—180
volts
provides
the
—470
volts.
However,
for the unregulated
4-350-volt output, the
connection
is
mode
ol the center tap
(4-
145 volts) of the
bridge
tthe
midpoint
ot the
—290
volts).
Adding
the
-f180
and
4-145
volts
provides the desired out-
put of
-r325 volts.
+
225-Volt Supply. The
voltage source for the regulated
-f-225-volt
supply
is
the
unregulated •4325-volt supply
described
in
the preceding paragraphs,
The
regulotor
circuit
is
similar to the
regulator
circuit
found
in
the
-150-volt
supply; the
moin
difference being thot instead of using o
glow
dischorge tube
os a
reference voltage
source,
the
referer»cc
voltage
is
from
the
—
550-volf supply.
The
error
signol
is
picked
off the junction of precision resistors
R60O
ond
R681.
The upper end
of R680
is
connected
to the
4-225-
volt output,
and
the
lower end
of R681
is
connected
to the
regulated -150-volt
supply.
The voltage
at
the junction
between R680 and
R68I
is
opproximotely
0.1
volt
which
is
applied through R682 ond
R6^
to
the grid of V684B. The
cathodes
of
V684
are
longfailed to the
—
150-volt supply
ihrough R685.
The
grid of
V684A
is
grounded.
The error
signal
is
fed from the grid
of
V684B
through
the
common-
cathode
circuit to
the
A
side
of the
tube.
Notice
that
this
comparator
is
somewhat
different
from
the
comparator
used
in
the
—
150-volf
supply,- the
output
is
token from the
A
side.
The
error signal
is
ompiified by V684 and
fed,
unchanged
ond
in
phase, to the voltage
divider
in
the grid
of
V694. V694
olso omplifies
and
inverts
the
error signol
and
opplies
it
out of phose with any chonge
in
the t225-
volf
output,
to
the grids of series regulators
V677B and
V737B.
Here ogoin,
the screen of the error amplifier
is
acting os
an
injection grid for ripple reduction.
A
sample
of the
unrcguloted supply
ripple
is
applied to the
screen of
V694.
V694
amplifies the
ripple, inverts
if
in
phose, and
applies
it
to the grids o*
series regulators
V677B and
V737B. The
result
is
that the
some
ripple
appears
simultaneously on the
grids
ond
plates of
V677B ond
V737B,
but
180°
out of
phase; thus the ripp'e
cancels
out.
-|-350-Volf Supply. The
input to
the 4-350-volt supply
is
the
full
voltoge output
of
the
center-topped
bridge
(see
description of unregulated
4-325-volf supply)
added
to
the
unregulated
side of the 4-100-volt supply.
The operation
of
the regulator
circuit
is
very
similar to
the operation
of
the
4-100-volf regulator except
for different
component
values.
-|-500-Vol} Supply.
Rectified
voltage from terminals 20
and
21 of T601
via 0762
is
added
to the reguloted voltage
ol the 4-3S0-volt supply
>o supply the
necessory voltage
for
the 4-500-volt supply- The operation of
the regulator
circuit
is
similof to thot of the
4-100-volt regulotor
except
for
dif-
•'erent
component
volues.
Crt Circuit
The
crt circuit (see Crt
schematic diagram)
includes the
crt, rt>e
high-voltogo
power
supply,
and
the controls neces-
sary
to focus Of*d orient
tfie
display.
The
crt
(Tektronix
Type
T5470-31-2)
is
on
aluminized,
5-inch, flat-faced,
gloss
crt
with
o
holicol oost-accelerotor
and
electrostatic
focus
and
deflection.
The
crt
circuit
provides connections
for
externally
modulating
the
crt
coihode.
The
high-voltage
power
supply
is
composed
of
a
dc-to-50-kc
power
converter,
o voltoge
regulator
circuit,
and
three
high-voltoge
outputs,
Front-panel
controls
in
the
crt circuit
adjust
the trace rotation (screw-
driver adjustment),
intensity, focus,
and
ostigmotism.
In-
terna! con'fols
adjust the
geometry ond
high-voltogo output
'evei.
3-3