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-
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
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
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