Pulse Shaper and Amplifier Circuit-CONT.

TM 11-6665-209-40

(6) The length of time that V104 conducts is determined by the R-C time constant

of C112 and the selected resistance path to ground. Four separate paths to

ground are provided, one for each range. These paths consist of resistor R 1 2 8

a n d calibrating potentiometer R 1 2 9 for the 500 mR range resistor R 1 2 6 a n d

calibrating potentiometer R127 for the 50 mR range resistor R123 a n d

calibrating potentiometer R124 for the 5 mR range and resistor R118 a n d

c a l i b r a t i n g potentiometer R119 for the 0.5 mR range.

(7) When V104 reverts to cutoff, the drop in its cathode potential, directly coupled

to the cathode of V103, permits V103 to again conduct its steady-state current.

Since the average time between successive pulses from the detector circuit is

considerably longer than the time that V104 conducts, the entire circuit reverts

to its steady-state condition after each pulse.

(8) The output of V104 is a series of current pulses and is fed to the indicator cir-

cuit. The duration of the V104 output pulses is determined primarily by the.

selected V104 grid-to-ground time constant circuit, and is thus fixed for any

one particular range. Switch section S102B inserts a different resistance for

each range in the grid-to-ground time-constant circuit, so that the duration of

the output pulse changes when ranges are changed,

(9) The pulse fluctuations of emitter potential of transistor Q105 occur across

resistor R125 and are applied to an attenuating network consisting of resistor

R122 and capacitors C109 and C111. The AC component of the fluctuations is

attenuated by C111, R122, and C109. This voltage is then applied to jack J101

on the front panel. Headset H-43B/U can be connected to this jack for aural

m o n i t o r i n g of the radiation intensity.

(10) The filaments of tubes V103 and V104 are provided with 1.2 volts AC from a

secondary winding on transformer T101. This voltage is supplied in all posi-

tions of S102 except OFF. A center tap on the winding is connected to

g r o u n d through common-cathode resistor R107.

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