Figure 3-14. Frequency-Time Recorder RD-88A/TMQ-5, Bottom View Showing Main Chart Dive Items.

TM 11-6660-204-25

EL6660-204-25-TM-36

Figure 3-14. Frequency-Time Recorder RD-88A/TMQ-5, Bottom View Showing Main Chart Dive Items.

c. Single Tube Substitution Method.

locate the trouble. It is then necessary to install new

(1) Substitute a new tube for one of the sus-

tubes, one at a time, until the equipment becomes

operative. This should be done as follows:

pected original tubes. If the equipment continues to

(1) Remove one of the suspected original tubes.

be inoperative, replace the new tube with the origi-

Install a new tube. If the equipment is still inopera-

nal. Similarly check each original tube suspected, one

tive, leave the new tube in place and remove the next

at a time, until the defective tube is located and the

suspected original tube. Install another new tube.

equipment becomes operative. Discard the last origi-

Mark the original tubes with the socket numbers

nal tube removed from the equipment. Do not leave a

from which they were removed. Continue this proce-

new tube in a socket if the equipment operates satis-

dure until the equipment becomes operative. The last

factorily with the original tube.

original tube removed is defective and should be dis-

NOTE

carded.

The oscillator circuit of tube V304B in the

(2) To determine whether another original tube

receiver may function with one tube and

is defective, return one of them to its original socket.

not with another, even though both tubes

If there is no noticeable difference in performance,

are good. If practical, retain any removed

leave the original tube in the equipment. In the same

tube until it is checked by suitable test

way, return the remaining tubes to their sockets, one

equipment.

at a time. If equipment failure occurs, or performance

(2) If this method of tube substitution does not

suffers, discard the last original tube installed. Do

correct the trouble, try the method described in d

not leave a new tube in a socket if the equipment

below.

operates satisfactorily with the original tube.

d. Multiple Substitution Method. Occasionally,

e. Turn-In for Repair. If none of the procedures

two or more tubes are defective in a piece of equip-

outlined above restore the equipment to normal oper-

ment. In such cases, the procedure in b above will not

3-20

Change 3