Tektronix 511 Instruction Manual page 22

voltage divider R90 and R91 places the tube on
the correct portion of its operating curve. So
that the screen dissipation will not be excessive,
the screen voltage is supplied through R95. C45A
keeps the potential relatively constant when sig ­
nals are applied to the control grid.
C AUTION - ALTHOUGH THE PROBE IN­
TRODUCES A SIGNAL ATTENUATION
OF 10 TIMES, IT SHOULD NOT BE CON­
NECTED TO CIRCUITS
VOLTAGES EXCEEDING 600 VOLTS.
Input Attenuator
All signals and calibrating voltages pass
through a four position, RC compensated attenua­
tor having attenuation ratios of 1, 2, 4 and 8 .
If a conventional resistance voltage divider is
shunted by capacitors whose values bear the
inverse ratio to the resistor values, the at­
tenuation is independent of frequency. The at­
tenuator is designed to have an input resistance
of 1 meg shunted by 40 ppf for all positions.
Since the input circuits to the amplifiers and
deflection plate are arranged to present 1 meg
shunted by 40 pjiif, the values chosen for the
attenuator are such that correct operation is
obtained when these values are in parallel with
the shunt arm. The capacitors, C32, C35, and
C38, shunted across the attenuators have no
effect on the attenuation ratio but are adjusted
so as to keep the input capacity at 40
Vertical Amplifier
The Type 511A contains a wide range two-
stage vertical amplifier with a switching ar­
CAUTION--THE SCALES OF THE CAL.
VOLTAGE CONTROL INDICATE PEAK-
TO-PEAK VOLTS, NOT RMS. MULTI­
PLY RMS BY 2.828 TO CONVERT TO
PEAK-TO-PEAK.
The Type 511A (S/N 2406 and up) calibrator
waveform is derived from the line-frequency
voltage of a 280 volt T1 secondary winding. The
positive peak is clipped (limited) by the diode
connected section of a 12AT7, V16.1. The point
of limiting is determined by the setting of the
CAL. ADJ. potentiometer, R75.4. Since the
P A G E 3 - 6
WITH PEAK
CALIBRATING CIRCUITS
+ 225 volt regulated supply, the point of limiting
put voltage is held within +or-5% of full scale
by employing a six step precision voltage divider
able output voltage from each range is obtained
from the CAL. VOLTAGE potentiometer which
T Y P E 5 1 1 - C I R C U I T
rangement so that only one stage may be used
if desired. The first stage which is used only
in the 2 STAGES position of the INPUT CHAN.
SEL. switch uses a 6AG7 tube V16.
The output stage is a cathode coupled, push-
pull 6AG7 stage, providing approximately 110 v
of undistorted output. The operation of this stage
is the same as that of the sweep amplifier stage.
The use of a push-pull stage is required to
give sufficient output and maintain the average
potential of the deflection plates constant so as
to prevent defocussing the beam. Low frequency
compensation is provided to correct for the
effect of the coupling capacitors. The resistors
R110 and R125 along with the capacitors C51A
and C51B provide a rising low frequency char­
acteristic together with a phase correction.
To take up variations in the component values,
the grid resistor R116 is made adjustable. The
procedure for this adjustment is given in Section
5. The inductances, L7, L8, L9 and L10provide
the high frequency compensation. A four ter­
minal coupling network is used to give the
greatest possible bandwidth. Every precaution
has been taken to obtain the smallest stray
capacities consistent with good mechanical con­
struction.
To increase the undistorted deflection when
observing pulses of a particular polarity, pro­
vision is made in instruments S/N 845 and up
to move the operating point of the push-pull
output amplifier from its normal position to
one which allows almost the entire output
swing to be utilized in either one direction or
the other.
voltage across R75.4 is obtained from the
is not affected by line voltage variations from
105 to 125 volts, thus the accuracy of the out­
for these line voltage variations. This limited
waveform is applied to the cathode follower
section of V16.1 which clips the negative peak
and provides six ranges of calibrating voltage
as the cathode follower load. Continuously vari­
D E S C R I P T I O N