When the TRIGGER SEL. switch is in the -INT
or +EXT. positions, signals are taken off the
cathode of VI and do not change in polarity.
Therefore a positive impulse must be supplied
by the external source or vertical amplifier
as the case may be. With the TRIGGER SEL.
in the + INT. or -EXT. positions, signals are
taken off the plate and reversed in polarity,
thus providing the required positive output from
negative trigger sources.
Trigger Amplifier
The 6AG7 tube, V2, serves to amplify and
invert the positive trigger impulses received
from VI. The TRIGGER AMPL. potentiometer,
R6, varies the bias and thus controls the point
on the positive trigger waveform at which V2
begins to conduct. R12 in conjunction with
C4A (C3) furnishes the small amount of cathode
bias necessary when the TRIGGER AMPL.
potentiometer is operated in its extreme clock
wise position.
Trigger Coupling Diode
The negative trigger impulses from the plate
of V2 are impressed on the plate of V4 by
means of the coupling diode V3. The diode is
used in preference to a coupling capacitor be
cause it disconnects the trigger amplifier from
the multivibrator once the multivibrator is trig
gered. When the multivibrator is triggered the
plate of V4 falls, making the diode plate nega
tive with respect to its cathode and therefore
non-conducting. This condition is maintained
until the multivibrator completes its cycle and
is ready to be triggered again.
Multivibrator
To convert the various shapes of trigger
impulses into square waves of controllable
duration, suitable for operating the sweep gener
ator and unblanking the cathode-ray tube, a
multivibrator is provided. This consists of two
tubes V4 and V5. During the waiting period V5
is fully conducting since its grid is at cathode
potential and therefore its plate is held at a low
value due to the voltage drop in R23. With V5
in this condition and the SWEEP STABILITY
correctly adjusted, the grid of V4 is held well
below the cut-off by the voltage divider, R17
and R18. The circuit remains in this condition
until a trigger impulse is received. The plate
of V4 is driven down by the trigger pulse and
also the grid of V5, because of the coupling
capacitor C7. The plate of V5 therefore rises
carrying with it the grid of V4 causing it to
conduct. This action continues until V4 is
conducting and V5 cut off. This condition is
maintained until the capacitor C7 discharges,
raising the grid voltage of V5 to such a point
that it starts to conduct. This makes the plate
of V5 fall, carrying with it the grid of V4 and
starting a regenerative cycle which ends with
V5 conducting and V4 cut off, the condition
which existed before the trigger impulse o c
curred. Thus the plate of V4 produces a square
negative pulse and simultaneously the plate of V5
produces a positive pulse. The negative pulse
is used to control the operation of the sweep
generator and the unblanking of the cathode-ray
tube. The positive pulse is used to furnish the
plus and minus GATE voltages available at the
front panel binding posts.
In instruments S/N1406 and up, the duration of
the time V5 is cut off is determined by the time
constant of C7, R20C, R20C1 through R20C9 (de
pending upon the position of S10A).The voltage
applied across the circuit is substantially inde
pendent of the characteristics of the trigger im
pulse. To cover a range of sweep time from .1
sec to 1 microsecond, C7 has five values as
selected by the SWEEP RANGE switch. The cali
brated variable resistor R20C is returned to
+ 225 volts. This makes possible the use of a lar
ger value of C7 than would otherwise be possible,
thus reducing the voltage divider action of the
stray capacitances to ground in the grid circuit
of V5. Variation of R20C, R20C1-9, in conjunc
tion with the five values of C7 gives a continuous -
ly variable adjustment of multivibrator pulse
length.
In instruments S/N101 to 1405, the duration
of the portion when V5 is cut off is determined
by the time constant R20A, R21, R22,C7 and the
voltage applied to R20A, and is substantially in
dependent of the characteristics of the trigger
impulse. To cover a range of sweep time from
.1 sec. to 1 microsecond, C7 has five values as
selected by the SWEEP RANGE switch. In the
three slowest positions R20A is returned to
ground, but for the two fastest it is returned
to +225 v. This makes possible the use of a
larger value of C7 than would otherwise be
possible, thus reducing the capacity voltage di
vider action of the stray shunt capacities to
ground of the grid circuit of V4. Variation of
R20A in conjunction with the five values of C7
gives a continuously variable adjustment of the
P A G E 3 - 2
T Y P E 5 1 1 —C I R C U I T D E S C R I P T I O N
Summary of Contents for 511
Page 1: ......
Page 4: ......
Page 5: ......
Page 26: ......
Page 52: ......
Page 58: ...Fig 5 6 Interior view right front side S N 845 1405 TYPE 511 A 511 AD SECTION 4 PAGE 22 ...
Page 60: ......
Page 61: ......
Page 62: ......
Page 63: ......
Page 66: ...Fig 5 14 Video Amplifier top S N845 1459 Fig 5 15 Video Amplifier bottom S N845 1459 ...
Page 68: ...Fig 5 18 Power Supply bottom view S N 845 1629 Fig 5 19 P ow er Supply top view S N 845 1629 ...
Page 72: ...DEGREES OF PHASE SHIFT Fig 5 27 SN 845 and up TEKTRONIX INC 12 28 50 ...
Page 97: ......
Page 98: ......
Page 101: ...AA ...
Page 102: ...SWEEP MAGNIFIER SWEEP AMPLIFIER c r r c r r s c ...
Page 105: ...TYPE 5IIAD CATHODE RAY OSCILLOSCOPE S N 2406 4 UP A A ...
Page 106: ... 2 2 5 V VERTICAL AMPLIFIER ...
Page 107: ...TYPE 511 CATHODE RAY OSCILLOSCOPE S N 101 454 AA POWER SUPPLY ...
Page 108: ...TO S7 3 A 6 6 117 V 60 APR 1949 S N 455 2405 A A ...
Page 111: ...4 A A C n o c n n r ...
Page 113: ......