HP 212A - Voltage Supply

volts depending upon setting of the AMPLITUDE control.
A flat-top
pulse is now formed for application to the output amplifier V11.
V11
is biased well beyond cutoff. As a result of the high bias voltage only
the top portion of the clipped pulse generated by Vb is passed through
V 1 1. The very high bias on V 1 1 removes unwanted signals of low am -
plitude that would otherwise appear on the baseline fallowing the output
pulse. See items 24 and 25 in trouble shooting chart.
The body of the final output pulse depends upon sufficient power from the
high voltage supply to maintain high initial pulse amplitude.
A droop in
in
the pulse body generally indicates a defective component in the high-
voltage supply.
See item b of trouble shooting chart.
If the pulse contains peaks or humps above the normal level of the top,
it would
indicate ineffective clipping, see items 7 and 8 of trouble shoot-
ing chart.
When
the top has a gradual rise or drop, the correction may
be a matter of adjustment and is covered in item 11 of the trouble shoot-
ing chart.
Trailing Edge -- V16 the 'stopt thyratron, 'turns off' the output pulse.
When V16 is triggered, it forms the trailing edge of the pulse. The trig-
g er pulse for the stop tube is developed by the circuits of amplifier 107a,
multivibrator V 1 OS and blocking oscillator V l09a.
The condition of the
trailing edge is the result of all these circuits, plus V8 which is In series
with 'stop' thyratron V16. The effects of these circuits can appear only
-
on the trailing edge of the output pulse. See items 13 and 14 of trouble
s hooting chart.
t'Both'Edges of Output Pulse -- If a trouble such as 'jitter' appears on
both leading and trailing edges of the output pulse, the defect is generally
in a circuit which affects both start and stop thyratrons simultaneously.
All circuits preceding V107b, (V101 through V 106b) affect both leading
and trailing edges and do not affect one edge without affecting the other.
Pulse Length -- A change in pulse length caused by an increase or de-
crease in rate is generally due to one of the thyratrons.
In some thyratrons
-
there is a very small time lapse between the time the tube is triggered
and the time the gas is fully ionized. The degree of time lapse depends on
the duty cycle. This characterisitic causes the pulse length to vary with
rate. Generally, the time lapse increases with an increase in duty cycle.
If the start tube has this characteristic, an increase in pulse rate will
cause the output pulse to shorten.
If the stop tube has this characteristic,
the output pulse will lengthen with an increase in rate.
See item 17 of
trouble shooting chart.
High pulse rates tax both thyratrons to a greater degree than low rates.
The symptoms of a failing thyratron therefore become more noticeable at
higher pulse rates.