Circuit Description—475
Q1318 o ff by way of the feedback voltage to the base. The
voltage waveform at the collector of Q1318 is a sine wave
at the resonant frequency of T 1320. Q1318 remains off
during the negative half cycle while the field collapses in
the primary of T 1320. When the field is collapsed suffi
ciently, the base of Q1318 becomes forward biased into
conduction again and the cycle begins anew. The amplitude
of sustained oscillation depends upon the average current
delivered to the base of Q1318. The frequency of oscilla
tion is approximately 50 kilohertz. Fuse F 1318 protects
the +15 volts supply in the event the High-Voltage
Oscillator stage becomes shorted. C1318 and L1318 de
couple the +15 volt supply line and prevent the current
changes present in the circuit from affecting the +15 volt
regulator.
High-Voltage Regulator
Feedback from the C R T cathode - 2 4 5 0 volt supply is
applied to the base of Q 1306 through R1303A . Any change
in the level at the base of Q1306 produces an error signal at
the collector of Q 1306, which is amplified by Q1308 and
Q 1316 and applied to the base of Q1318 through the
feedback winding of T 1320. Regulation occurs as follows.
If the output voltage at the —2450 volt test point starts
to go positive (less negative), this positive-going change is
applied to the base of Q1306. Q1306 conducts harder,
which in turn causes Q1308 and Q1316 to conduct harder.
This results in greater bias current to the base of Q1318
through the feedback winding of T 1320. Now, Q1318 is
biased closer to its conduction level so that it comes into
conduction sooner to produce a larger induced voltage in
the secondary of T 1320. This increased voltage appears as a
more negative voltage at the —2450 volt test point to
correct the original positive-going change. By sampling the
output from the C R T cathode supply in this manner, the
total output of the High-Voltage Supply is held relatively
constant.
Q1312 and Q1310 compose an overvoltage protection
circuit. In the event the regulating action of the circuit
should cause the CRT cathode supply to approach approxi
mately —3000 volts, the voltage level at the emitter of
Q1316 will be very close to —6 volts. Normally Q1312 and
Q1310 are biased off and do not conduct. When the voltage
level at the emitter of Q1316 reaches approximately —6
volts, Q1312 is biased into conduction, which in turn biases
Q1310 on. Q 1310 now starts to reduce the base drive
(
i n t e n s it y
!
RI335
SWEEP
UNBLINKING
GATE
-----
CHOP
BLANKING
2 AXIS
AMP Q I3 32
''OUTPUT AMP
QI344 QI35H
01352
Q\35&
QI362
C I37I CRI379
R I378
HIGH VOLTAGE
OSCILLATOR
QI3I& TI320
REGULATING
AMP
Q I3 0 G Q13IO
Q 1 3 0 8 Q13I2.
Ql3Ko
CATHODE
SUPPLY
CRI320
C R I3 2 I
R 139*7
Fig. 3-9. Detailed block diagram of the C RT 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 ...
Page 189: ......
Page 190: ...4 T 475 OSCILLOSCOPE FIG 1 FRO NT PANEL ...
Page 191: ...475 OSCILLOSCOPE FIG 2 MAIN FRAME ...
Page 199: ......
Page 200: ...FIG 3 RIGHT SIDE l 475 OSCILLOSCOPE ...
Page 201: ...V S X O t l B O T T OVJ 8 8 ...
Page 209: ......
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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Page 241: ... 1 I R I II9A po S IT I o n f i n e I R l 130 PAGE 4 OF 5 R 1234 Ml 9 91 9 473 ...