Circuit Description—7D14
Feedback Amplifier
The
Feedback
Amplifier converts the Trigger Generator
differential
output to a single-ended signal to provide nega
tive
feedback to the Input Amplifier. This stage consists of
an integrated-circuit (IC) operational amplifier U161.
Feed
back
from
the
output of U161
at pin 6 is connected to the
minus input through
R161.
Slope
Switching
The
Slope Switching
stage connects the Trigger Genera
tor
differential output to
the Gate and Trigger Indicator
Pickoff
inputs. Slope switching is accomplished by
means
of relays K152-K252
(in conjunction with Q259), as deter
mined by the PRESET-VAR and SLOPE switches.
When
the PRESET button is in, positive (+) slope trig
gering
is selected,
regardless of the LEVEL SLOPE control
setting. This
sets
the
relays
to connect the Trigger
Gen
erator
+ and
—
outputs to the Gate + and — inputs
respectively
(i.e., in phase).
When
the VAR
button
is in, the trigger slope is deter
mined by
the SLOPE switch
setting. In that SLOPE switch
position, the
circuit operation is the same as described
for
PRESET.
When
the
SLOPE switch is set to —, +15 volts
applied
to
K252
and to the base of Q259 reverses the state
of the
relays; this reverses the
phase of the signal connec
tion
to
the Gate.
Trigger
Indicator
Pickoff
The Trigger
Indicator Pickoff stage consists
of Q855 and
Q859. This stage
provides an analog signal output to the
oscilloscope
through the Interface Connector to display the
Trigger
Generator output on the CRT. A Trig Out signal is
also
provided to trigger a time-base unit.
R866, Display Posi
tioning,
adjusts the output voltage levels to
set the vertical
position
of
the CRT display.
Gate
The
Gate stage consists
of input emitter-coupled pair
Q170-Q270, output emitter-coupled pair Q180-Q280, sig
nal
switches Q275-Q278, and tunnel-diode CR174. This
stage connects
the
differential signal at its inputs to the
Binary
Driver stage
on command of the complementary
GATE
and
GATE
inputs.
The
+
and — inputs to this stage are the bases of Q170
and
Q270 respectively. Reference
zener
diode VR178
establishes
a
low-impedance,
—7.5-volt reference level at the
base
of Q180. Decoupling for
the —7.5-volt reference level
is
provided by
C178. Reference zener diode VR176 estab
lishes
a low-impedance,
—2.5-volt reference level at the
cathode
of
tunnel-diode CR174. Decoupling is provided by
C176.
Signal switching
is accomplished by
connecting the
signal
at the collector
of Q270 through either Q278
or
Q275
as determined by the state of tunnel-diode CR174.
Tunnel-diode
CR174 must
be in its high state for Q275 to
be
forward
biased, and
in its low state for Q278 to be
forward
biased.
Tunnel-diode
CR174 is
switched into its high state when
GATE
is
HI
with respect to GATE (GATE "on") and Q170
is forward
biased. When tunnel-diode OR 174 is in its high
state, Q275 is
forward biased
to connect the
Q270-collector
signal
to the base
of Q280. Q180-Q280 act as a paraphase
amplifier to provide
a
differential-current output to the
Binary
Driver through T183.
When
GATE is
HI with respect to GATE (GATE "off"),
CR174
is switched back to its
low state, regardless of the
state of Q170. The
low
state of CR174 forward biases
Q278
and reverse biases Q275. This connects the Q270-
collector signal to
the low-impedance,
—7.5-volt reference
level point
to
turn off the Gate stage.
Binary
Driver
Q190-Q290 amplify the
differential-current input
from
the
Gate to
the current level necessary to provide
a Clock
output
to the Binary Counter (First Decade
Counter circuit). Diode-connected
Q288 provides a
temperature-compensated
voltage
level at the
bases of
Q190-Q290
and Q188. Q188 acts as a constant-current
source
to supply
the emitter current for Q190-Q290.
FIRST
DECADE
COUNTER
General
A detailed
block
diagram of the First Decade Counter
circuit
is shown in Fig. 3-4. An input/output table for the
First
Decade
Counter
circuit is
shown in Fig. 3-5. A
schematic of
this circuit is shown on Diagram
2 in the
Diagrams
section.
The
Binary Counter Voltage Regulator provides two
temperature-compensated
operating voltages to
the Binary
Counter
integrated circuit. These output voltages are
derived
from
the
oscilloscope —15-Volt power supply.
The
Binary Counter stage counts the Clock
input, and
provides
a binary-coded output.
The Binary
Counter output
provides the 2° bit of the BCD
output to the 10° Storage
3-6
Summary of Contents for 7D14
Page 4: ...7D14 ...
Page 11: ...Operating Instructions 7D14 Fig 2 1 7D14 front panel controls and connectors 2 2 ...
Page 33: ... 3 13 Fig 3 11 Logic diagram for Zero Cancel Logic stage Circuit Description 7D14 ...
Page 38: ...3 18 Fig 3 16 Time Base and Control circuit detailed block diagram Circuit Description 7D14 ...
Page 44: ...NOTES ...
Page 46: ...NJ Fig 4 1 Electrode configuration for semiconductors in this instrument I ...
Page 68: ...NOTES ...
Page 96: ... 7DI 4 DIGITAL COUNTER UNIT ...
Page 98: ...GRS 0371 BLOCK DIAGRAM ...
Page 99: ......
Page 103: ...0 0 I 200 mV 500 µs 0 001 200 mV 500 µs 0 001 MHz 00 mV E 00 µs 0 001 MHz ...
Page 106: ...1 ...
Page 110: ...A2 Logic Circuit Board Assembly jQ798i 798 jc743 CR744t uni R724 R742 JL744S FrR796 ...
Page 113: ......
Page 114: ...P 0 A2 LOGIC BOARD ...
Page 121: ... A B D t F H J NPR Tj ZWX V A AC M AEA HUM qAZ DEF HJ N P R S T J V V7X y ABM APAI AA 7DI4 ...
Page 129: ......
Page 130: ...4 7D14 DIGITAL COUNTER ...
