Tektronix 067-0521-00, Instruction Manual

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Circuit Description— 0 6 7 - 0 5 2 1 -0 0
Fig. 3-4. Timing relationship of waveforms during alternate-sweep
ing. Sweep rate of Time Base B is set twice as fast as Time Base A.
V102A, since if arrives af fhe same fime as fhe large nega­
tive Time Base B sync pulse through D102. No sync pulse is
received from the oscilloscope at the end of “ A ” sweep, thus
the composite signal af fhe cathode of V102A consists of
negative spikes which are alternately the sync pulse at the
end of + “ B” sweep, then the slave pulse at the end of “ A ”
sweep.
When V102B and B95A are conducting, the switching
multivibrator is set to display the upper trace (Time Base B
sweep). In this state, fhe negative slave pulse has no effect
on the multivibrator; since the pulse cannot pass through
D102, if is applied through V102A to fhe grid of V95B, which
is already cut off. However, when V102B and V95A are cut
off, the multivibrator is not set to display the upper trace.
In this case, if a slave pulse arrives, if will cut o ff V95B,
turning on V95A and resetting the multivibrator to be ready
to display the upper trace. Thus the upper trace always
slaving operation of oscilloscopes capable of alternate-sweep switch-
occurs immediately following the negative slave pulse and is
locked to the Time Base B sweep.
When the TEST FUNCTION switch is set to the CHOPPED
position, the voltage in the grid circuit of the switching
multivibrator sets the circuit for astable operation. See Fig.
3-5. The switching action begins as soon as supply voltages
are connected, due to slight characteristic differences be­
tween the A and B sections of the tube. The repetition rate
of the multivibrator in the Chopped mode is approxim ately
lOOkc, set by the supply voltages and the resistor-capacitor
combinations in the grid and plate circuits.
As the multivibrator switches from one state to the other,
one output signal is generated in the same manner as the
vertical switching signal in the Alternate mode as D89 turns
on and off. Each time V95A conducts, D89 and D90 are fo r­
ward biased and D89 shunts to ground any signal applied to
the EXT INPUT connector during the time that the upper trace
(D
3 -5