Impulse Generator Driver Stage V703B

(in series with R734 to ground) and

changes in current through the coil

capacitors C712, C713, and C714,

o p e r a t e s a mercury switch within

is connected in the grid-to-cathode

G 7 0 1 , which generates the 70-cps

circuit. Resistor R733 functions as

calibrating voltage by charging and

t h e grid return.

discharging a length of coaxial

cable that functions as a delay line.

(4) Dynamic circuit description. W i t h

c. Impulse Generator G701. T h i s a s -

S 7 0 5 in its ON position, regener-

sembly consists of a coil (b above) which

a t i v e voltage is coupled from the

surrounds a mercury switch, a coaxial

plate, pin 6, of V703A to the grid,

d e l a y line in series with current-limiting

pin 7, through capacitor C711 and

resistor R738, and discharge path re-

the frequency-determining net-

s i s t o r R 7 3 7 . Circuit action is described

work. The values of the frequency-

below.

d e t e r m i n i n g elements are chosen

s o that the regenerative voltage

(1) T h e coil surrounding the mercury

will be in phase with the grid volt-

switch is part of the plate load of

a g e at approximately 70 cycles.

impulse generator driver stage

The oscillatory output at the plate,

V703B. The 70-cps voltage devel-

pin 6, is coupled through capacitor

o p e d across the coil operates the

C716 to the input of impulse gen-

m o v i n g contact at a 70-cps rate.

e r a t o r driver V703B.

W i t h the contact at its normally

o p e n (NO) position, the coaxial

b. Impulse Generator Driver Stage

d e l a y line is connected through

V 7 0 3 B . This section of the dual triode

c u r r e n t - l i m i t i n g resistor R738 and

serves as a driver for the coil of impulse

f e e d t h r o u g h capacitor C723 to a

generator G701 and as a power amplifier.

B+ voltage determined by the set-

(1) P l a t e circuit. The plate, pin 1, of

t i n g s of the series-connected im-

V703B receives B+ potential

p u l s e generator step attenuators

through the solenoid coil of G701

S707 and S708. This B+ voltage can

and v 01 t a g e-dropping resistor

b e as high as 450 volts, positive

R729, with IMPULSE GENERATOR

or negative with respect to chassis

DB ABOVE 1 V/MC switch S705

ground, depending on the position

in the ON position.

o f c h ass is control POLARITY

(2) Cathode circuit. The voltage drop

switch S709 (fig. 6).

a c r o s s cathode resistor R736, at

(2) W i t h the contact at its normally

pin 3 of the tube, develops cathode

c l o s e d (NC) position, the coaxial

bias.

delay line is discharged to ground

(3) G r i d circuit. High value resistor

t h r o u g h resistor R737. The ????-

R735, connected between pin 2 of

s i e n t discharge of the dc voltage

the tube and chassis ground, is the

on the delay line produces a broad-

g r i d return.

band signal whose frequency spec-

t r u m is flat, within one-half db,

(4) Dynamic circuit description. T h e

f r o m 150 kc to 1,000 mc. This

70-cps voltage from V703A is ap-

spectrum corresponds with the

plied to the control grid, pin 2, of

frequency coverage of the test set

V 7 0 3 B . The solenoid coil of im-

and creates a usable source of

p u l s e generator G701, shunted by

c a l i b r a t i n g voltage which requires

c a p a c i t o r C717, forms the plate

no tuning of circuit elements.

l o a d . Capacitor C718 and resistor

R729 form a plate decoupling net-

(3) T h e t r a n s i e n t d i s c h a r g e o f t h e

work. Feedthrough c a p a c i t o r s

c o a x i a l delay line is de-coupled

t h r o u g h output connector P709 to

C 7 2 1 and C722 bypass transients

developed by the impulse generator

i n p u t jack J713 on coaxial relay

m e r c u r y switch contacts. The

K702 (fig. 14).