User's Manual

g. Adjust the SCREEN fine control until the SCREEN VOLTS

meter indicates the voltage specified on the tube test data roll chart

(par. 12).

h. Set the BIAS fine control to its extreme clockwise (maxi-

mum) position.

i. With the PRESS TO TEST P5 switch held in its operated

position, gradually reduce the bias voltage by adjusting the BIAS

fine control until the tube strikes its firing potential. The firing

potential is indicated by a sudden increase in load current shown

on the PLATE meter and by a sudden decrease on the PERCENT

QUALITY meter.

Note. The tube will not conduct (as indicated by an increase in load current

shown by the PLATE meter) until the critical grid-bias voltage is reached.

For example, for a type 2D21W or type 2050W tube, the bias voltage at which

conduction occurs should be between 1.5 and 3.0 volts.

j. The voltage at which the tube strikes is read on the GRID

BIAS VOLTS meter. Record the grid voltage at the instant and

at the point that the pointer starts to deflect. This is the striking

voltage of the tube under test. Repeat the test to confirm the read-

ing. Minimum limits for striking voltages of thyratrons are given

on the tube test data roll chart.

k. When the test is completed, set the ON-OFF power switch

to the OFF position, remove the tube under test from the test

socket, and return all switches and controls to their safety posi-

tions (par. 15d).

27. Electron-Ray Indicator Test

There are two types of electron-ray (ER) indicator tubes that

can be tested with the TV–2(*)/U, Type 6U5 and similar tubes

have a triode section and a single indicator (one shadow). Type

6AF6 and similar tubes have no triode section, but have twin

indicators (dual shadow).

Follow the procedure below to check

the opening and closing action of the eyes only. Indicators with

triode sections also must be tested for emission (i below).

a. Perform the operations indicated in paragraphs 15 and 16.

b. Operate the FUNCTION switch to the TEST position.

c, Operate the PLATE-SCREEN RANGE switch to the posi-

tion specified on the tube test data roll chart.

d. Adjust the PLATE and SCREEN fine controls until the

exact voltages specified on the tube test data roll chart are indi-

cated on the corresponding meters.

e. Depress the PRESS TO TEST P4 switch. If the tube is a

single indicator, the indicator should be closed; if the tube is a

twin-indicator tube, such as the 6AD6 or 6AF6, indicator No. 1

should be closed and indicator No. 2 should be open.