Tektronix Type 130, Инструкция по эксплуатации

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Circuit Description — Type 130
3-2
AA
is practically symmetrical, regardless of the frequency,
when the ADJ. 1 control is properly set.
The multivibrator is arranged to shift rapidly from one
stable state to a second stable state when the input grid
goes past a transition point. For example when the B
section of V70 is conducting its plate is down and divider
R73, R72 between plate and ground hold the A-section grid
below plate-current cutoff. The A-section plate will there-
fore be positive, and the common cathode voltage will
be determined only by current through the B-section. If the
B-section grid drops, its plate current will rise carrying the A-sec-
tion grid more positive, and the common cathode voltage
will drop placing the A-section grid-to-cathode bias nearer
to conduction.
When the input grid drops far enough it reaches the
transition point and the A section conducts thereby divert -
ing some of the cathode current from the B section. The re-
sulting positive signal at the plate further raises the A-
section grid. C73 bypassing R73 improves the ac trans -
mission so that a large positive signal reaches the grid and
raises the cathode so high that the B section of V70 is cut
off.
The plate of the A section generate a square pulse for
each cycle. The positive level of the square pulse is deter -
mined by diode-connected V76B at about +150 volts. The
bottom of the pulse is determined by cathode follower
V76A. The grid voltage of this cathode follower determines
the clipping level and provides a means of adjusting the
meter sensitivity on the 300-
μ
h and
μμ
f ranges. The adjust-
ment is labelled ADJ. 2 300.
Counter Circuit
The square pulses from the plate of multivibrator V70A
are applied to the left-hand end of one of the capacitors,
C90, C91, C92, C93 or C94, for example C90. Charge diode
V15B holds the right-hand end of C90 at about +150 volts
during the negative excursion while the multivibrator pulls
down the left hand end to about +100 volts, thus charging
C90 to about 50 volts.
During the positive excursion, the multivibrator raises
the left-hand end of C90 to about +150 volts and the right-
hand end thus goes above +150 volts toward +200 volts.
This places the plate of diode V45B above its cathode so
that it conducts and discharges C90 into the +150-volt
bus through the indicating meter.
The capacitor always charges completely to the same
voltage, so the current it discharges through the meter de-
pends linearly on how many times it discharges per second
and on the size of the capacitor. The range-selector switch
selects the capacitor sizes in ratios of about 3 to provide
ranges of 3, 10, 30, 100, and 300. The largest capacitor is
used for the lowest range to increase the quantity of charge
per cycle. Resistors R97, R98, R99 and R100 are adjustable
shunts across the meter, selected by the range switch to pro-
vide individual sensitivity adjustment. The 300 range has
no shunt and its sensitivity is adjusted by the negative-
peak-clamper grid voltage.
Power Supply
DC power is furnished by a full-wave rectifier and capaci-
tor filter. V403 is a voltage stabilizer that supplies the cir-
cuits likely to be affected by line-voltage variations. Heat-
ers of all tubes are biased halfway between ground and
+150 volts to reduce the heater-to-cathode voltage of
several cathodes that operate at +150 volts.
The transformer primary has two equal 117-volt windings
that are normally connected in parallel for 117-violt service.
For 234-volt service, they can be connected in series.
The range selector switch opens the input to the primary
in the OFF position.