(3) Grid bias voltage is supplied to the
e. Voltage-Regulator Tube Test Circuit. T h e
quality of voltage-regulator tubes, gas rectifier
tube under test by full-wave rectifier
tubes, and other gas-filled tubes is determined by
tube V2. The bias voltage is indicated
measuring the regulation of the tube under test
by grid BIAS volts meter M2.
under varying load conditions. The voltage drop
(4) The potentials made available by the
across the tube under minimum and maximum
power supply are fed to the various
load conditions is indicated on PERCENT
test sockets through seven electrode
QUALITY meter M3. PRESS TO TEST P5
Selectors switches, and to the tube
switch S20 selects the voltage regulator test.
test circuits through test position press
f. Filament Continuing Test Circuit. This test
to test switches P1 through P6.
provides visual indication of the continuity
b. Transconductance (G,,,) Test Circuit. T h i s
check of the filament of hot cathode tubes, bal-
circuit gives an indication of the overall merit
last tubes, indicator lamps, and other filament-
of amplifier tubes under simulated operating
type devices. If the filament of the device under
conditions by measuring the transconductance
test is continuous, FIL. CONT. SHORT indi-
(G,,,) of the tube under test. Indication in per-
cator lamp 12 will light. The test is selected by
cent quality is shown on PERCENT QUALITY
operating PRESS TO TEST P1 switch S16.
meter M3. The test is selected by operating
g. Short Test Circuit. Interelectrode shorts in
PRESS TO TEST P4 switch S19.
the tube under test are detected by this circuit,
which is basically the same as the filament con-
detectors, vacuum-tube rectifiers, and multiele-
tinuity test circuit. A short between any two
ment tubes is checked by measuring the dc emis-
elements of the tube will light FIL. CONT.
sion under static conditions. PRESS TO TEST
SHORT indicator lamp 12. SHORT TEST
P2 switch S17 is used to check diode emission;
switch S11 is used to select any tube electrode
P2 switch S17 and P3 switch S18 are used simul-
and test it for shorts to all other elements.
taneously for multigrid emission.
h. Leakage Test Circuit. L e a k a g e b e t w e e n
d. Gas Test Circuit. This circuit is used to
the elements of an electron tube is detected by
check the presence of excessive amounts of gas
this circuit, which is essentially a simple ohm-
in vacuum-type tubes by indicating the shift in
meter circuit. The leakage between the elements
the operating points of the tubes because of gas
of the tube is indicated in megohms on PLATE
current in the grid circuit. The test is performed
meter M5. Each position of the SHORT TEST
by operating PRESS TO TEST P6 switch S21
switch selects one element of the tube for meas-
with the transconductance test.
uring the leakage to all other elements.
AGO 1428A
5
