of plate current and a reduced voltage drop
age of the tube under test is indicated on GRID
across the tube. The ionization or striking volt-
BIAS VOLTS meter M2.
TM6625-316-35-8
Figure 8. Voltage regulator and thyratron tube test circuit of Test Set, Electron Tube
T V - 2 ( * ) / U , Simplified schematic diagram.
potential at points 1 and 2 is increased until
9. Short Test Circuit
FIL. CONT. SHORT lamp 12 lights. Actually,
an effective resistance of 3,000 ohms or less
a. A simplified schematic diagram of the cir-
across resistor R61 is sufficient to light the FIL.
CONT. SHORT lamp.
cuit used for detecting interelement shorts in
b. When PRESS TO TEST P1 switch S16 is
the tube under test is shown in figure 9. A por-
in its normal unoperated position and FUNC-
tion of the bias voltage is taken from bias recti-
TION switch S4 is in the TEST position, SHORT
fier tube V2 and applied to a bridge network
TEST switch S11 is connected across resistor
formed by resistors R35, R60, R61, and R62. The
voltage at point 1 is constant and depends only
R61. Selection of any one of the electrodes, ex-
cept the filament in the tube under test, is made
on the bias supply voltage and on the values of
resistors R35 and R62. The voltage at point 2
through the front portion of section 1 of switch
is a function of the bias supply voltage and the
S11. If a short circuit exists between the fila-
values of resistors R60 and R61. When no ele-
ment and any other element of the tube, the rear
ments of the tube under test are short-circuited,
of section 1 of switch S11 completes the circuit
to ground, and thus shorts out resistor R61 and
the difference in potential between points 1 and
causes FIL. CONT. SHORT lamp 12 to light.
2 is below the striking voltage of FIL. CONT.
The selection of the cathode of the tube under
SHORT lamp 12. When there is a short circuit
test by the f rent of section 1 of switch S11 will
between elements of the tube under test, the
voltage at point 2 is reduced. Because the volt-
test for a short circuit between the cathode and
age at point 1 is constant, the difference in
filament.
AGO 1428A
13
