Tektronix 516 series, Instruction Manual

Page: 21 / 132

Circuit Description — Type 516
tion of probes. The Power Supply supplies regulated voltages
and currents as required throughout the oscilloscope.
The remainder of this section of the manual presents a
more detailed description of the operation of each of the
oscilloscope circuits. Throughout the discussion, you should
refer to the circuit diagrams contained in the Diagrams sec­
tion of this manual.
VERTICAL AMPLIFIER
The Vertical Amplifier of the Type 516 Oscilloscope con­
tains two separate Input Amplifier Channels (A and B), a
common Output Amplifier, and a Switching Circuit. Signals
may be applied to both Input Amplifier Channels, and the
Switching Circuit makes it possible to display one signal
as a single trace on the crt or to display both signals as
two separate traces. It does this by turning the outputs
of the two Input Amplifier Channels alternately off and on,
either on alternate sweeps of the trace or at a 150-kHz
switching rate.
The Type 516 can also be used as a conventional single­
channel oscilloscope with an input signal on one channel
only.
A block diagram of the Vertical Amplifier is shown in
Fig. 4-2.
Input Amplifier Channels
Since the two Input Amplifier Channels are identical, ex­
cept for the CHANNEL A GAIN SET adjustment, the follow­
ing discussion refers to the A Channel only. Operation of the
B Channel is identical.
The signal to be displayed is applied through the PO­
LARITY switch and the VOLTS/DIV. control to one of the
grids of the Input Cathode Follower, V423. When the PO­
LARITY switch is in either of the AC positions, the signal is
coupled through C400 which prevents the dc component of
the signal from being applied to the Input Cathode Follower
grid. When the POLARITY switch is in one of the NORM,
positions, the signal is applied to the grid of V423A and is
displayed on the crt in the normal position, with the positive
portions toward the top of the screen. When the POLARITY
switch is in one of the INV. positions, the signal is applied
to the grid of V423B and is displayed on the crt in the in­
verted position, with the positive portions toward the bottom
of the screen.
A
INPUT
CONNECTOR
B
INPUT
CONNECTOR
4 - 2
Fig. 4 -2 . V ertical A m p lifie r block diagram .