Short Test

(7) Adjust the FILAMENT fine control until the FILA-

MENT VOLTS meter needle indicates 6.3 volts.

b. Short Test. T o p e r f o r m t h e s h o r t t e s t ( p a r . 1 8 ) o n t h e

6SQ7 tube, proceed as follows:

(1) For the TV2/U, aline the dot on the PLATE fine control

with the dot on the panel. For the TV-2A/U and TV-

2B/U, aline the PLATE fine control pointer-type knob

with the line index marking on the panel.

(2) Turn the SHORT TEST switch slowly from the OPER.

position to V, W, X, Y, and Z, and back to OPER.; at

the same time, tap the tube with a finger and watch the

FIL. CONT. SHORT indicator lamp.

(3) If the lamp glows continuously or glows during tapping

in any of the five positions of the SHORT TEST switch,

t h e tube contains a short circuit. Discard the tube. If

there is no short circuit, proceed with the next test.

c. Interelement Leakage Test. To perform the test for interele-

ment leakage (par. 19) on the 6SQ7 tube, proceed as follows:

(1) Set the FUNCTION switch to the LEAK position.

(2) Set the PLATE meter, which is functioning as an ohm-

meter for this test, to zero (par. 19c).

(3) Turn the SHORT TEST switch slowly from the OPER.

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

for a deflection of the PLATE meter pointer.

(4) An open circuit or zero leakage between elements will

produce no deflection of the PLATE meter pointer. A

short circuit between elements will produce a full-scale

deflection of the pointer. Read intermediate values on

the resistance scale of the PLATE meter. If there is no

leakage, proceed with the next test.

(5) Set the FUNCTION switch to the TEST position.

d. Filament Continuity Test. Proceed as outlined below to de-

termine whether the filament of the 6SQ7 tube is open (par. 20).

T h e FIL- and FIL+ SELECTORS switches are set as indicated

in the tube test data roll chart, at 7 and 8, respectively.

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

(2) Depress the PRESS TO TEST P1 switch.

(3) If the FIL. CONT. SHORT lamp glows, the filament is

good. If the lamp does not glow, the filament is open.

Discard the tube. If the filament is good, however, pro-

ceed to test the transconductance of the triode section.

(4) Set the SHORT TEST switch to OPER.