Tektronix 511A-AD, Instruction Manual, Page: 11 / 75

With the EXT. SWEEP ATTEN. fully clockwise the de­
flection sensitivity is approximately 1.5 volts per cm DC
or peak
to peak
AC.
VERTICAL DEFLECTION SYSTEM
The Type 511 A is equipped with a very flexible ver ­
tical deflection system capable of amplifying or attenu ­
ating as necessary a wide range of waveshapes. Since
the best amplifiers and attenuators have faults, it ap­
peared undesirable to first attenuate large signals and
then amplify them back to something like their original
size. It was therefore decided that the Type 511 A should
have a switching system so that only as much amplifi­
cation as needed to get a reasonably sized image would
be employed. This switch called the INPUT CHAN.
SEL. has four positions, DC, VIA COND, 1 STAGE and 2
STAGES. In the DC position the SIGNAL INPUT con­
nector is connected via the INPUT ATTENUATOR to the
upper deflection plate without a coupling capacitor.
The lower plate is connected to the VERT. POSITION
control and bypassed for signals. The VIA COND. posi­
tion is similar to the DC except a .1 mfd capacitor is in
series with the deflection plate. On these two positions
the deflection sensitivity is approximately 27 V per cm
DC or peak to peak AC, with the attenuator in the X 1
position.
Normally, connection to the SIGNAL INPUT is accom ­
plished by attaching the Binding Post Adapter, which is
supplied, and a single lead. When reduced loading on
the circuit under test is desired, the Input Probe should
be used.
CAUTION — THE PEAK POTENTIAL AP­
PLIED TO THE PROBE SHOULD NOT EX ­
CEED 600 VOLTS.
Since the probe introduces an attenuation of 10X, it
will be advantageous to employ a common shielded
lead
(no
attenuation) to
prevent pickup
of stray fields
when dealing with very low signals, if the additional
circuit loading is permissible. A ground lead to the
equipment under observation should be provided, and
often an earth ground is desirable.
Vertical Amplifier
With the INPUT CHAN. SEL. switch in the 1 STAGE
position the SIGNAL INPUT connector is connected
to
the
deflection plate via
the
INPUT ATTENUATOR, a
cathode follower, the VERT. AMPL. ATTEN., and a one
stage push pull amplifier. The VERT. AMPL. ATTEN. is
a 500 ohm potentiometer in the cathode of the cathode
follower, allowing the gain of the amplifier to be con ­
tinuously adjusted over a range of two to one, thus fill­
ing in the INPUT ATTENUATOR steps. Both low and
high frequency compensation is employed to produce
a wide band of uniform amplification. Careful attention
has been paid to the transient response so that square
wave pulses, etc. will be faithfully reproduced. The
amplifiers are adjusted at the factory for optimum tran­
sient response rather than flat frequency response. A
much flatter response is obtainable if desired by in ­
creasing L6, and readjusting L7, L8, L9, and L 10 , but
overshoot will occur on steep wave fronts. With opti ­
mum transient response, the rise time (10% to 90% of
full amplitude) is .04 microseconds or better. At the low
frequency end of the band, the top of a 10,000 micro ­
second square pulse will not depart by more than 5%
from flatness. The deflection sensitivity is approximately
2.7 V per cm peak to peak maximum.
CAUTION— CARE MUST BE TAKEN TO
AVOID OVERLOADING THE AMPLI­
FIERS. THIS WILL BE AVOIDED IF THE
IMAGE IS NOT ALLOWED TO EXCEED
THE RULED SECTION OF THE GRATI ­
CULE, WITH THE VERT. POSITION CON­
TROL SET SO THAT WITH NO SIGNAL
APPLIED THE SWEEP LINE IS CENTERED.
In the 2 STAGES position a wide band pre-amplifier
stage is inserted between the INPUT ATTENUATOR and
cathode follower. Since the bandwidth and transient
response of the two stage amplifier are inferior to a sin­
gle stage amplifier, this position should not be used un­
less it is necessary, in order to obtain a sufficiently large
image. Rise time is .05 microseconds. The gain of the
two stage amplifier is about 100, making the maximum
deflection sensitivity approximately .27 V per cm peak
to peak.
The deflection polarity is inverted when the 2 STAGES
position is used, resulting in downward deflection on
the CRT for positive input polarity.
A three position lever type switch mounted at the rear
of the Type 511-A permits the operating bias on grid No.
1 of V19 to be varied. With the switch set at the center
(normal) position, the bias applied to V 19 is equal to
the bias of V18, resulting in balanced operation and
equal upward and downward undistorted deflection of
the trace. For normal operation, the DEFLECTION
POLARITY switch should be in this position.
If it is desired to observe pulses, the switch should be
set in either the upward or downward position, corres ­
ponding to the deflection of the image on the cathode
ray tube.
In
the
upward position,
the
bias of V 1 9 is de­
creased, resulting in increased output of V 1 9 and de ­
creased output of V 18, thus permitting greater undis ­
torted upward deflection. These conditions are reversed
when the deflection polarity switch is in the downward
position.
Direct Connection to Deflection Plates
To allow direct connection to the deflection plates
with the lowest capacity, banana jacks are provided on
a panel accessible through an opening in the left side
of the case. By removing the jumpers the internal
cir­
cuits may be disconnected. The terminal marked Y1 is
the top plate and the one marked X2 is the right plate.
Deflection sensitivity is approximately 27 V DC per cm
on the vertical plates and 32 V per cm on the horizontal.
If positioning control is desired, the jumpers should
be replaced with 1 megohm resistors and a series cou­
pling capacitor employed. Unless balanced input is de ­
sired, the unused deflection plate should be bypassed
to
ground.
SECTION 2, PAGE 3 TYPE 511-A, 511-AD