Tube Testing Techniques

TM 11-6660-204-25

Item

No.

Item

Action or Condition

Normal Indications

Corrective Measures

If one or two advance speed

Set at 2 (RD-88C) only).

Chart advances 2-inches per

for the RD-88C are incor-

minute.

rect, inspect/repair the me

chanical chart drive mecha

nism.

Rawin time-print (TPO).

Replace S503 or C502.

Set to OFF.

Control recorder TPO (Time

AUTO.-OFF-MAN

Print-Only) does not oper-

switch (If the recorder is

ate for any pen position on

not connected to the ra-

the scale.

win sat, omit this test.)

Set to AUTO.

Check circuits of S503 and

Control recorder produces

S504. Adjust setting of

TPO when pen exceed 89 to

S504.

91 chart ordinates.

Replace S503.

Depress switch to MAN.

Control recorder produces

TPO each time switch is de-

pressed.

POWER switch.

R e p l a c e POWER switch

Set POWER switch.

Jewel power indicator lamp

S201.

goes out and VOLTAGE

and FREQUENCY meters

indicate zero.

(3) Remove the rear panel to provide access to

3-24. Tube Testing Techniques

tubes.

When trouble occurs, check all cabling, connections,

(4) To remove rectifier tubes V401 and V408 and

and the general condition of the equipment before

series regulator tubes V402 and V409 mounted on

attempting to remove the electron tubes. Isolate the

the power supply chassis, release the safety clamps

trouble, if possible, to a particular unit or section of

around the base of the tube before pulling the tube

the equipment. Gain access to the suspected tubes

from it's socket. Be sure that the safety clamp is

and follow the procedures as outlined in b below. If

tightened after the new tube has been placed in the

tube failure is suspected, and a tube tester is not

socket.

available, proceed as outlined in c below if this proce-

b. Using Tube Tester.

dure fails to clear the trouble, follow the procedure

(1) Remove and test one tube at a time. If it is

outlined in d below.

necessary to remove more than one tube at a time,

CAUTION

label each one so that it may be replaced, if satisfac-

Do not rock or rotate the top of a miniature

tory, in its original socket.

tube when removing it from its socket;

(2) Replace a tube only when there is an obvious

pull it staight out. Rocking or rotating

defect, such as a broken glass envelope, open fila-

the tube causes the pins to bend and may

ment, broken lead, or connecting prong, or when a

break the weld where the pin enters the

test in a tube tester or other equipment shows the

glass. A high resistance or intermittent

tube to be defective.

joint also may develop. If tube pins get

(3) Do not discard a tube because it tests on or

bent, staighten them in the sockets pro-

near the minimum test limit of the tube tester. Some

vided for that purpose in the bottom of the

new tubes test near the low end of the acceptability

cabinet.

range of the tube specifications. These tubes provide

satisfactory service over a long period of time, even

a. Access to Tubes. To gain access to tubes for

though they remain at or near this low limit value.

testing or replacement, proceed as follows:

(4) Do not discard a tube merely because it has

(1) Operate the POWERLINE circuit breakers

been in use for a specific length of time. Satisfactory

to the OFF position.

operation in a circuit is the final proof of tube quality.

(2) Remove the rear panel retaining screws at

the rear of the cabinet.

3-19

Change 3