Gas Test

d. A d j u s t t h e P L A T E a n d S C R E E N f i n e c o n t r o l s u n t i l t h e

PLATE and SCREEN VOLTS meters indicate the exact voltages

specified on the tube test data roll chart. Red calibration marks

on both meters facilitate this adjustment.

e. S e t t h e B I A S R A N G E s w i t c h t o t h e v o l t a g e o r p o s i t i o n

s p e c i f i e d on the tube test data roll chart.

f. A d j u s t t h e B I A S f i n e c o n t r o l u n t i l t h e G R I D B I A S V O L T S

m e t e r indicates the exact grid-bias voltage specified on the chart.

g. If the bias voltage indication is over 80 percent of full scale

at a low plate voltage setting, it may be difficult to obtain the

required bias voltage. In such a case, use the next higher setting

of the BIAS RANGE switch.

h. O p e r a t e t h e q u a l i t y S H U N T c o n t r o l t o t h e n u m b e r g i v e n o n

the tube test data roll chart.

i. A d j u s t t h e P E R C E N T Q U A L I T Y m e t e r t o z e r o ( p a r . 1 7 ) .

j. O p e r a t e t h e G M - S I G N A L R A N G E s w i t c h t o t h e p o s i t i o n

specified for the quality test.

k. Adjust the SIGNAL-V.R. fine control until the pointer of the

SIGNAL meter is on the red line.

l. Depress the PRESS TO TEST P4 switch to its locking posi-

tion.

m. Read the percent quality for the tube under test on the

PERCENT QUALITY meter.

(1) If the reading is below the minimum limit indicated on

the tube test data roll chart, discard the tube.

(2) If the reading borders on the minimum limit, the tube

may be usable but should be replaced soon.

(3) If the PERCENT QUALITY meter indication is beyond

full scale, the tube may be gassy. Perform the gas test

n. Release the P4 switch.

Note. A multisection tube may be listed several times on the tube test data

roll chart. If this is the case, reset the SELECTORS switches for each

listing in the tube test data roll chart. Repeat the short test and the trans-

conductance test for each new setting.

o. When a test is completed, set the ON-OFF switch to the OFF

position, remove the tube under test from the test socket, and

return all switches and controls to their safety positions (par.

22. Gas Test

U s e the following procedures to determine whether an amplifier