H O R IZ O N T A L A M P LIFIE R
General
The Horizontal Am plifier circuit provides the output
signals to the CRT horizontal deflection plates. The signal
applied to the input of the Horizontal Amplifier is
determined by the T IM E /D IV switch. The signal can be a
sawtooth waveform generated within the instrument, or
some external signal applied to the CH 1 OR X input
connector (X -Y mode of operation). The Horizontal Amp
lifier also contains the X 1 0 magnifier, horizontal posi
tioning controls, and some beam finder circuitry. Fig. 3-7
shows a detailed block diagram of the Horizontal Amplifier
circuit. A schematic of this circuit is shown on Diagram 10
at the rear of this manual.
Input Paraphase Amplifier
Q1124 and Q 1 134 form the Input Paraphase Amplifier.
This is an emitter-coupled amplifier stage that converts the
single-ended input signal to a push-pull output signal. The
X 10 Magnifier circuitry is in this stage and consists of a
divide-by-ten attenuator R 1106-R 1107-R 1108. When the
X 10 Magnifier is on, the input signal is applied unattenu
ated to the Input Paraphase Amplifier. When the X I 0
Magnifier is off, the input signal is applied to the Input
Paraphase Amplifier through the attenuator. X 1 0 MAG
indicator DS1110 lights when the X 10 Magnifier is being
used. C R 1121 and CR1122 lim it signal amplitudes at the
input to the amplifier to prevent amplifier overdrive.
Q1140 is a relatively constant current source for Q1124
and Q1134. C R1140 provides temperature compensation
for the base-emitter junction of Q1140. RT1123 varies in
value with changes in temperature to compensate for
associated changes in amplifier gain. Magnifier Registration
adjustment R1130 balances quiescent DC current in Q 1124
Circuit Description—475
and Q 1 134 so that a center screen display does not change
position when the X 1 0 Magnifier is turned on.
Q1114 is a current-source that is an interruptable path
for the horizontal positioning currents. When the T IM E /
D IV switch is in any position other than X -Y , the anodes of
C R 1103, C R 1104, and CR 1111 are connected to —8 volts
through R 1104, which reverse-biases them. In the X -Y
position of the T IM E /D IV switch, +5 volts is connected
directly to the anodes of C R 1103, C R1104, and CR 1111.
This accomplishes three things. First, the emitter-base
junction of Q1114 is reverse biased which prevents the
Horizontal POSITION and FIN E controls from having any
affect on the display. Second, relay K1103 is energized
which connects the X-axis signal from the Channel 1
Preamplifier to the input to the Horizontal Amplifier.
Third, +5 volts is connected to the Channel 1 Scale Factor
Switching circuit so that both deflection factor indicators
are operating. When operating in the X -Y mode, R1102
adjusts for correct X-axis gain and L 1 103 adjusts to reduce
the phase differences between the horizontal (X) and
vertical (Y ) signal paths.
Gain Setting Amplifier
Q1152 and Q1162 are an emitter-coupled push-pull
amplifier stage. The gain of this stage is adjusted to match
the C R T sensitivity. When the BEAM F IN D pushbutton is
pushed R 1 168 is switched into the circuit: This reduces the
dynamic swing capabilities of this stage, thereby limiting
horizontal deflection to within the limits of the C RT
viewing area. Q1152 and Q1162 operate in an overdriven
mode. This means at the extremes of signal amplitude, one
side will be turned o ff while the other side is still
conducting. This condition generates some common-mode
signal differences between Q1152 and Q1162. Q1164
monitors any common-mode signal differences (through
R1165 and R 1167) and conducts to minimize them.
S I 0 5 0
S IIIO
®
3-15
Fig. 3-7. Detailed block diagram of the Horizontal Amplifier.
Summary of Contents for 475
Page 6: ...475 475 Oscilloscope ...
Page 20: ......
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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 211: ...4 4 75 O S C ILLO S C O P E FIG 5 CAB IN ET ...
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