HP 212A - Circuit Description; General; And Blocking Oscillator

SECTION ZIL
CIRCUIT DESCRIPTION
GENERAL
The Model 212A Pulse Generator consists of three basic parts, the
triggering circuits which are located in the front deck, the main pulse
generating circuits, and the power supply which are located in the
rear deck.
The block diagram of the triggering and main pulse gen-
eratin'g circuits are shown in Figure 3-1.
A11 of the triggering cir-
cuits are located to the left of the thyratrons V6 and V16.
This block
diagram and the schematic wiring diagram will both be referred to in
the following circuit description.
3-2 REP. RATE MV
This section of the circuit consists of an amplifier, phase inverter,
and
a multivibrator.
The amplifier tube V103A and the phase inverter tube
V103B in conjunction with switch S102A are used to deliver a negative
pulse to the input of the multivibratoP.
The repetition rate multivibrator consists of tube V104AB and may be
operated either free running or triggered by an external pulse. In the
free running condition it generates pulses at the repetition rate of 50-
5000 pulses per second or in the externally synchronized condition it
may be externally triggered up to 5000 pulses per second.
When the rnultivibrator is externally synchronized, it is biased so
that it generates a pulse only when triggered by the external pulse.
The pulses generated by this multivibrator are supplied to the delay
multivibrator and the pulse position multivibrator.
3-3 DELAY MY AND BLOCKING OSCILLATOR
Tube VlOlAB is employed as a "one shot1' multivibrator, The pulse
from the repetition rate multivibrator triggers the delay multivibrator
to produce a positive 15 microsecond pulse which is inverted by VlOZA.
The trailing edge of the 15 microsecond pulse then triggers the block-
ing oscillator.
The blocking oscillator tube V102B forms the sync out pulse which is
supplied to the sync out terminals of the instrument through a polarity
reversing switch.