User's Manual

3A6GT 3Q4

3B7

3Q5QT

3D6 3S4

3LF4

3V4

d. If the lamp burns continuously or glows during tapping in

any one of the five positions of the SHORT TEST switch, the tube

contains short-circuited electrodes. Discard the tube unless an

exception is noted on the tube test data roll chart.

e. Disregard a momentary flash of the FIL. CONT. SHORT

indicator lamp while the SHORT TEST switch is being moved

from one position to the next. This flashing usually is caused by

the charging of a capacitor in the test circuit.

Note. Some tubes normally test as shorted when the SHORT TEST switch

is in certain positions. Before discarding a tube that shows a short, check

the tube test data roll chart NOTES column for information on normal short

indications.

f. When the 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.

15d) .

19. Interelement Leakage Test

Follow the test procedure in a through e below to determine the

interelement leakage (LK) in megohms between electrodes of the

tube under test.

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

b. Operate the FUNCTION switch to the LEAK position. This

position connects the PLATE meter into the circuit to serve as an

ohmmeter for this test only.

c. Set the ohmmeter (PLATE meter) to zero as follows:

(1) Operate the SHORT TEST switch to the V position.

(2) Turn the PLATE fine control to its maximum counter-

clockwise position.

(3) Depress the PRESS TO TEST P1 switch.

(4) With the P1 switch held in its depressed position, adjust

the PLATE fine control until the pointer of the PLATE

meter indicates zero (250 on center scale) on the ohm-

meter (top) scale.

(5) Release the P1 switch.

d. Operate the SHORT TEST switch slowly from the OPER.

position to positions V, W, X, Y, and Z; at the same time, watch

for a deflection of the PLATE meter pointer.