Section Il. GENERAL THEORY

Section Il. GENERAL THEORY

pally of a power supply to furnish the correct

3. Block Diagram Analysis

voltages to the tubes under test, a line test cir-

(fig. 2)

cuit, an-d five tube-testing circuits. These five

The block diagram illustrates the several ma-

circuits are shorts, noise test, rectifier test,

jor circuit sections of the test set and their

mutual conductance test, and gas test. Controls

relation to each other. Voltage from a 115-volt

and switches permit the application of proper

alternating current (at) power source is re-

test voltages to the tube under test, and a meter

duced and standardized by the operation of the

or an indicating lamp displays the test results.

line adjust circuit. For line voltage adjust-

The relationship among the principal circuits

ments, pushbutton 1 -- LINE ADJ. is de-

and parts of the test set are shown in the block

pressed. Voltage is then applied to meter M101

diagram (fig. 2).

through metallic rectifier CR101. When the

a. Power Supply (fig. 3). The power supply

meter pointer is directly over the LINE TEST

consists of three supply voltage circuits, each

mark, the voltages for the test circuits are

supplied by transformer T101.

standardized.

(1) The filament suppIy consists of second-

a. The power supply circuit consists

ary windings No. 7 and FILAMENT

basically of transformer T101 and rectifier

VOLTAGE switch S108. The FILA-

tubes V101 and V102. The power supply pro-

MENT VOLTAGE switch is used to

vides ac voltages for the mutual conductance

select any one of 18 different filament

tests and for the filaments or the heaters of

voltages for the tube or panel lamp

V101, V102, and the tube under test, and pro-

under test, ranging from 0.6 volt to

vides direct current (de) voltages for the tube

117 volts ac. PILOT lamp E102 is

under test. Voltage is applied to the tube under

connected between terminals 22 and

t e s t through FILAMENT VOLTAGE switch

28 of secondary No. 7, and lights when

S108 and the selector switches.

the POWER switch is set to the ON

b. Pushbutton switch assembly S110 pro-

position.

vides a selection of various combinations of

(2) Full-wave rectifier tube V101 supplies

plate, screen, bias, and signal voltages that are

unfiltered, pulsating dc voltage for the

required to test the different types of tubes.

plate of the tube under test. Second-

Proper selection of these voltages is made

aries No. 1 and No. 2 supply the ac

through the setting of the selector switches

voltage for the plates of V101. Fila-

before the voltages are applied to the tube under

ment voltage for V101 is supplied by

teat. The selector switches determine the test

secondary No. 6.

socket terminals to which the various test volt-

ages are applied. The FUNCTION SWITCH

(3) Grid bias voltage and screen grid volt-

age is supplied to the tube under test

serves a dual purpose: when shorts tests are

b y full-wave r e c t i f i e r tube V102.

m a d e , positions No. 1 through 5 of the

Secondaries No. 4 and No. 5 supply

SHORTS section of the FUNCTION SWITCH

permit the application of an ac voltage to the

t h e operating voltages for V102.

Various amounts of bias voltage for

different elements of the tube under test. When

the tube under test can be selected by

p o s i t i o n s A through E (A through F, TV-

changing the setting of the BIAS con-

7D/U) of the RANGES section of the FUNC-

TION SWITCH are used, the sensitivity of

trol. A separate winding on trans-

former T101 supplies an ac signal

meter M101 and the magnitude of the signal

voltage are controlled. Meter M101 indicates

voltage to the grid circuit of the tube

the condition of the tube under test.

under test. Screen grid voltage may

be varied by adjusting the taps on

4. Function of Equipment

resistor R130. Pushbutton 2 -- DIODE

Test Set, Electron Tube TV-7(*)/U employs

permits either the normal screen grid

the dynamic mutual conductance method to test

voltage or a low screen grid voltage

amplifier tubes, The test set consists princi-

to be applied to the tube under test.