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Circuit Description— Type M
around the secondary, driving the base in a positive direc
tion in excess of that needed to turn off the transistor. The
base and emitter return to their original level and transistor
Q6350 remains cut off until the next sync trigger arrives to
repeat the cycle.
The signal at the emitter of Q6350 is a single regenerated
negative-going pulse that occurs each time the sync trigger
from the oscilloscope is applied to the Q6350 collector
circuit. This regenerating of the sync triggers standardizes
the varying size and shape of the sync triggers originating
from various types of oscilloscopes. The regenerated trigger
becomes a sharp negative-going spike when coupled
through C6352 and is easily handled without jitter by the
Ring Counter.
(3 ) Free-running operation.
The Switching B.O. free
runs when two or more channels are on and the ALTER-
NATE/CHOPPED switch is set to CHOPPED. When the
switch is in this position, one side of the switch disconnects
pin 8 of the interconnecting plug from ground, disabling the
oscilloscope sync amplifier.
The other side of the ALTERNATE/CHOPPED switch dis
connects the R6365/R6366 divider from R6367 and connects
it to the emitter circuit of Q6350. Transistor Q6350 base-
emitter junction becomes slightly forward biased. Diode
D6360 is still forward biased and D6352 reverse biased.
As soon as Q6350 conducts, the regenerative action of
T6350 drives Q6350 rapidly into saturation. During this
action, C6353 charges rapidly through the low emitter im
pedance.
At saturation, Q6350 collector current is constant and
the T6350 field collapses. The collapsing field generates a
positive-going backswing signal at the base, and the base
returns quickly to its original level. Capacitor C6353 dis
charges through R6353 and the emitter returns to its original
positive potential. When this happens, Q6350 conducts
again, repeating the cycle. The repetition rate of the Switch
ing B.O. is approximately 1 me and is determined mostly by
the R6353-C6353 time constant.
The negative-going signal at the emitter of Q6350 is
coupled through C6352 to drive the Ring Counter. The
signal at the base of Q6350 is a negative-going pulse
with a duration of about 0.2 microsecond. The pulse ends
with a positive-going backswing caused by the inductive
kick in T6350. Normally, the backswing is undesirable.
However, during chopped-mode multi-trace operation the
backswing is useful as a blanking pulse to blank out the
switching transients on the displayed waveform.
The positive-going backswing at the base of Q6350 drives
D6352 into conduction.
The diode serves two purposes
during chopped-mode multi-trace operation—to limit the
amplitude of the backswing, and to couple the backswing
to the base of Q6364.
S /N 101-824
Chopped-Mode Blanking Amplifier
During multi-trace operation when the ALTERNATE/
CHOPPED switch is set to CHOPPED, the Chopped-Mode
Blanking Amplifier Q6364 amplifies and inverts the back-
swing signal. The Q6364 collector circuit, during this mode
of operation, has the following configuration. The ALTER
NATE/CHOPPED switch grounds the switch end of collector
load resistor R6364. The other end of R6364 is connected
to the collector through D6364, which is forward biased
because Q6364 is conducting.
Diode D6368 is reverse
biased since its cathode return ties to +100 volts within
the oscilloscope.
The signal developed across R6364 is coupled through
C6364 and pin 16 of the interconnecting plug to the blank
ing amplifier in the oscilloscope time-base generator cir
cuit. From there it is applied to the cathode of the ert
via the CRT Cathode Selector switch. The signal blanks the
beam during the switching-time interval occurring between
channels.
Blanking the beam during this time prevents
the unwanted switching transient from appearing on the
displayed waveform.
During either single-trace or multi-trace chopped-mode
operation, diode D6368 is reverse biased when the M Unit
is used with a single-beam or a Type 555 dual-beam oscillo
scope. When the M Unit is used with a Type 551 dual-beam
oscilloscope having a multi-trace plug-in unit in the other
plug-in compartment, D6368 remains reverse biased when
the other unit operates in a chopped mode, to isolate the
two plug-in units. If the other unit in a Type 551 operates
in an alternate mode, pin 8 is grounded and D6368 is for
ward biased. Although D6368 is forward biased, the diode
has no important function during this mode of operation.
When the ALTERNATE/CHOPPED switch is set to ALTER
NATE, diode D6364 is reverse biased. This prevents sync
triggers from getting to the collector of Q6364, and pre
vents Q6364 from loading down the incoming sync.
HEATER CIRCUIT
The heaters in the Type M Plug-In Unit are supplied with
direct current from the - f 100-volt regulated supply in the
oscilloscope. This prevents the possibility of 60-cycle cathode
modulation, which might result if the heaters were supplied
with alternating current.
Power for the heater circuit (+75 v at 150 ma) is ob
tained from pin 15 of the interconnecting plug. For those
oscilloscopes employing Delaying Sweep, the heaters of two
of the tubes in the Delaying Sweep Generator are connected
in series with the heater circuit of the M Unit to provide the
necessary 25-volt drop. In those instruments employing only
one Sweep Generator, a resistor connected between the
heater string and the + 100-volt bus provides the required
drop.
The heater circuit also provides constant voltage sources
for many circuits in the M Unit. The +13.6 volts developed
across Zener diodes D5392 and D5393 (D5390 S/N 101-
3479) goes to the circuit of Q5344, Q5354, Q6350 and the
base circuits of the transistors in the Ring Counter. The +6.3
volts developed across Zener D5391 goes to the base circuits
of Q5334 (four channels). (S/N 101-824— the + 3 8 volts goes
3-6
Содержание M 531
Страница 43: ...RIGHT SIDE Parts List Type M http manoman sqhill com...
Страница 45: ...Parts List Type M LEFT SIDE 0 0 0 IP 6 6 http manoman sqhill com...
Страница 56: ..._____________ CHANNEL A __________ SIGNAL OUTPUT AMPLIFIER 1 t y p e m p l u g i n u n i t AI...
Страница 64: ...TYPE M TENT SN 9660 CHANGE TO Q5344A B ELECTRICAL PARTS LIST CORRECTION 151 0232 00 Silicon Dual M15 594 170...