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d ) Trigger coupling
In the DC mode, relay contact K851 is closed and the signal is passed unattenuated via R868.
In the LF mode, K851 is open and switch contact S20C is closed. The signal is now passed via the series low-
pass filter R872, C858, R869.
In the HF mode, K851 is open and switch contact S20D is closed (moving contact t o earth). The signal is now
passed via the high-pass filter C858, R872. Both in LF and HF modes, the d.c. component is blocked by C868.
In the AUTO PP mode, the trigger signal is a.c.-coupled (K851 is open).
Only in the external X deflection mode together with AUTO PP mode can d.c. coupling be selected.
If T T L trigger mode i s available on the instrument, the signal is always d.c.-coupled (K851 closed).
This
signals for the TOP DETECTOR, T V CIRCUITand X DEFLECTION AMPLIFIER.
The INTERFACE also produces symmetrical output signals for TRIGGER VIEW and the FINAL TRIGGER
AMPLIFIER.
The asymmetrical voltage signal from the TRIGGER COUPLING
FET source-follower
LEVEL control R6. As
which can be varied by the LEVEL control.
The source-follower V887 is followed by an emitter-follower D853 (9,10,11) (6,7,8) with
source V859. As the emitter-follower transistors are part of one IC,
characteristics for these transistors. This technique is featured widely in the MTB and DTB trigger circuits.
An asymmetrical current signal for external X deflection is picked-off from D853-11 and routed via the switch
unit to the horizontal channel switch on the time-base unit.
Another asymmetrical current signal i s taken from D853-6 end is routed via shunt feedback amplifier V863 to
the TOP DETECTOR and the T V CIRCUIT.
The symmetrical output voltage signal i s available on D853-10 and D853-7, and applied to series feedback
channel switch to facilitate trigger view.
The signal available on D853-10 and D853-7 is also applied to the series feedback amplifier D853 (12,13,14)
and 0853 (1,15,16). The common current source for this
potential applied to R996 via selection switch S20A. In the external X deflection and T V trigger modes this is
switched off and R996 floats.
In the T T L trigger mode (optional) the amplification of this stage is increased as relay contact K852 closes.
The symmetrical output current signals are available on D853-12 and D853-1 and have phase shift of 180 degrees.
Depending on the position of the
Selection i s by switching diodes: V888, V889 for the
I f the
Transistor V896 i s not conducting
switches on diode V857 and the signal from D853-1 leaks away. Diode V858 is blocked and the connection
between D853-1 and the MTB is interrupted.
I
-
I f the
any signal
so
I n this event, transistor V896 conducts because the positive-going base potential and switches off transistor
to the input of the MTB.
receives
i t s
input signal from the DC, LF, HF trigger coupling and produces asymmetrical output
stage
stage
result, the source outputs of V887 show
a
+
slope is selected (S8 open), V889 blocks and the signal from D853-12 i s routed via V888 to the MTB.
-
slope is selected (S8 closed), V889 conducts, so the signal from D853-12 leaks away. Diode V888 blocks
this point is also prevented from reaching the MTB.
a t
gate
of V887 receives a d.c. voltage that can be adjusted with the
stage is
+/-
SLOPE switch S8, one of the two signals i s used for MTB triggering.
+
slope, V857, V858 for the - slope.
transistor V897 switches on. The positive potential on i t s emitter
so
diode V858 conducts and the output signal on D853-1 collector is routed
so
is applied to one
of the symmetrical
stage
gate
symmetrical voltage signal, the level of
a
common-current
a
results in better stability and closer-matched
it
a
symmetrical current signal t o the vertical
D853 (2,3,4), switched on by an earth
2-1 5
stage
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