Circuit Description—475
offset compensation changes associated with variations in
ambient temperature. As temperature increases, the value
of R T170 decreases. This results in a decrease in voltage
across CR170 and C R174. C R170 and CR174 are voltage-
variable capacitance semiconductors whose capacitance
increases with a decrease in reverse voltage across them.
Thus, CR170 and C R174 will provide more peaking at
higher temperatures. L178 is a toroid inductor that cancels
high-frequency common-mode signals generated by the
previous stages. The Channel 1 Position Centering adjust
ment centers the range of control of the Channel 1
POSITION control.
CHA NNEL 2 PREAMP
General
The Channel 2 Preamp circuit is virtually the same as the
Channel 1 Preamp circuit. Only the differences between the
two circuits are described here. Portions of this circuit not
described in the following description operate in the same
manner as for the Channel 1 Preamp circuit. Fig. 3-3 shows
a detailed block diagram of the Channel 2 Preamp circuit. A
schematic of this circuit is shown on Diagram 2 at the rear
of this manual.
First Cascode Amplifier
Basically, the First Cascode Amplifier stage in Channel 2
operates as described for the First Cascode Amplifier stage
in Channel 1. However, the Channel 2 First Cascode
Amplifier also contains the IN V E R T switching function.
This allows the Channel 2 signal to be inverted as displayed
on the C RT. The IN V E R T switch, when pushed, changes
the biasing on the output transistors of U220 so that the
normally inactive transistors are now carrying the signal.
Since their outputs are cross-coupled from side to side the
output signal is of opposite polarity to that available in the
normal (button out) position of the IN V E R T switch. The
Channel 2 Invert Balance adjustment R215 adjusts the DC
balance of the stage to eliminate baseline shift in the
display when switching from a normal to an inverted
display.
V E R T IC A L CHA NNEL SWITCHING C IR C U IT
General
The Vertical Channel Switching Circuit determines
whether the Channel 1 or the Channel 2 Preamp signal or
both will be connected to the Vertical Output Amplifier
circuit. In the A L T and CHOP modes of operation, both
channels are alternately displayed on a shared-time basis.
The Vertical Channel Switching Circuit also provides several
internal trigger signals to the Trigger Generator circuits, the
Channel 2 V E R T S IG N A L O U T signal to a connector on
the rear panel, and the chopped blanking signal to the Z
Axis Amplifier. Fig. 3-4 shows a detailed block diagram of
the Vertical Channel Switching Circuit. A schematic of this
circuit is shown on Diagram 3 at the rear of this manual.
Channel Switch 1C
The Channel Switch 1C, U 370, determines which of the
Preamp signals will be passed to the Vertical Output
Amplifier. The push-pull Preamp signals connect between
pins 2 and 3 (Channel 2) and between pins 10 and 11
CH2
j
v o l ts
/
d iv
"! *
S20B
CH2 VERTICAL
SIGNAL TO
VERTICAL
CHANNEL
SWITCHING
CIRCUIT
®
3-5
Fig. 3-3. Detailed block diagram of the Channel 2 Vertical Preamplifier circuit.
Summary of Contents for 475
Page 6: ...475 475 Oscilloscope ...
Page 20: ......
Page 46: ......
Page 151: ...A B C D E F G Fig 7 4 P 0 A4 Vertical Mode Switch circuit board ...
Page 152: ...n m m m 1 t siumm c ii im ...
Page 154: ...Diagrams 475 A B C D E F G ...
Page 155: ...GRID LOCATOR Fig 7 8 P O A3 Vertical Preamp circuit board ...
Page 157: ...Diagrams 475 ...
Page 158: ...GRID LOCATOR 2 3 4 5 6 7 8 9 1 10 11 1 12 Fig 7 10 P 0 A3 Vertical Preamp circuit board ...
Page 160: ...Diagrams 475 GRID LOCATOR Fig 7 11 A5 Vertical Output circuit board ...
Page 163: ...Diagrams 475 GRID LOCATOR Fig 7 12 P O A8 Trigger Generator And Sweep Logic circuit board ...
Page 167: ... 415 OSCILLOSCOPE B T R IG G E R G E N E R A T O R g B TR IG G E R GEN ER A TO R ...
Page 168: ...Diagrams 475 GRID LOCATOR ...
Page 172: ...SWEEP G E N ER A TO R S ...
Page 175: ...TIM IN G HORIZONTAL DISPLAY SWITCHING ...
Page 177: ...A 011 HORIZONTAL AMPLIFIER 8 l j k J Ll J Ol Z o N C O X U 1 C L O o v O o _J V v P O in r ...
Page 179: ... 476 OSCILLOSCOPE ...
Page 180: ...POWER SUPPLY ...
Page 182: ...CRT CIRCUIT ...
Page 185: ...C A L IB R A T O R A N D F A N C I R C U I T 4 C A LIB R A TO R FAN MOTOR C IR C U IT ...
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Page 190: ...4 T 475 OSCILLOSCOPE FIG 1 FRO NT PANEL ...
Page 191: ...475 OSCILLOSCOPE FIG 2 MAIN FRAME ...
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Page 200: ...FIG 3 RIGHT SIDE l 475 OSCILLOSCOPE ...
Page 201: ...V S X O t l B O T T OVJ 8 8 ...
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Page 210: ...5 ...
Page 211: ...4 4 75 O S C ILLO S C O P E FIG 5 CAB IN ET ...
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