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GAIN ADJ Control adjusts the overall gain by
varying the amount of feedback. The HORI
ZONT
AL
POSITIONING Control positions the
trace by varying the voltage on the grid at
V 24 1 . Wafer 3 R of the PLATE-GRID selector,
S W 20 5 , positions the beam to the right in the
GRID position.
CRT-DIS PLAY SWITCHING D I AGRAM
The CRT -Display Switching diagram shows
the PLATE-SCREEN-GRID Control in detail
with the associated circuitry shown in block
form.
The PLATE-GRID Control and the
VOLTS/DIY attenuator resistor are shown in
the horizontal- amplifier block to show the
p at h of the load current drawn by this resistor.
The Floating, unregulate d, Power Supply
shown at the left of the diagram is an auxiliary
power supply.
Its only return to ground is
through SW5 1 0 - 5 R which connects it to the
cu rrent measuring resistors in the GRID and
S C R E E N positions of this switch.
In the GRID position of the PLA TE-SCREEN
G RID selector, the F loating Power Supply is
connected to circuits in the Step Amplifier
which supply current to the grid of the device
under test.
'
In the SCREEN position of the
P L ATE-SC REEN-GRID selecto r , the F loating
Power Supply is connected to the
+
DC- circuit
s e ries regulator and the current which flows
through the current measuring resistors in
s c reen current.
In the P L ATE position of
the PLA TE-SCREEN-GRID selecto r , the Float
ing Power Supply remains connected to the series
regulato r , but it is now disconnected from the
c urrent measuring resistors and grounded by
S W 5 1 O .
The P l ate- Sweep Generator i s also
an
u ngrounded supply.
It is connected to the
cu rrent measuring resistors in the PLATE
position o f the PLATE-SCREEN -GRID selector
b y SW51O-5R.
In the other two positions of
this switch the Plate- Sweep Generator is ground
ed.
The Horizontal Amplifier is connected to the
plate or the grid of the device under test by the
P L ATE-GRID selector.
If the VOLTS/DIY
attenuator resistors were grounded, current
drawn by this resistor would pass through
the current measuring resistors of the Vertical
Amplifier.
To avoid this , a section of the
P L ATE-GRID selector connects the ground
return back to appropriate places on the PLA TE
S C RE E N - G RID selector.
V E RTICAL AMPLI F I E R D IAGRAM
M A / D I V Switch
The MA/DIV switch selects the resistance to
ground in the current measuring circuit and
thus selects the sensitivity of the measurement.
The grid of the Input Amplifie r
t
V 28 1
t
is
connected to R255 instead of the arm of the
s witch to prevent any error that might be
c aused by contact resistance. R254 maintains
a current path at all times as the switch is
rotated between positions . Fuse F 255 added
at serial number 500 1 - up protects the high value
resistors in the attenuator but is shorted out
in the high-current positions of the switch.
A m plifiers
The Input Amplfiers . V281 and V280, are
common cathode
t
phas e - splitter amplifiers.
R270 positions the crt display vertically by
v arying the voltage on the grid of V280. C280
limits the bandwidth of the input stage to main
tain stabi lity with the feedback used.
The
V E RT GAIN ADJ Control varies the gain by
changing the amount of negative feedback. The
Output Amplifiers provide the additional gain
n ecessary to drive the crt deflection plates.
Plate-Sweep and Meter Circuit D i a g r a m
T r a n s f o r m e r
The plate -sweep transform e r . T3 1 0 ,
is
s upplied from taps on the primary of the main
power transform e r . T40 1 . Both primary and
s econdary windings are shielded to provide max
imum control over capacitive currents. The
P LATE T RANS CURRENT B ALANCE Contro l ,
C 3 1 5 , b alances the stray capacitances t o ground
which are associated with this winding. These
currents would otherwise flow in the current
m easuring circuits.
S E R I ES LOAD Control
Full- wave rectification of the incoming sin
usoidal waveform occurs in V 3 1 5 and V 3 1 6 .
The resulting waveform i s applied t o the plate
of the tube under test by way of the S E RIES
LOAD switch. In the 300 ohm position of this
3 - 4
C ircuit Description - Type 570
AA
Summary of Contents for 570
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