TM 11-6625-599-12
umn. When using the checklist in b b e l o w ,
3-11. Equipment Performance Checklist
follow each step in order. If the corrective
a. General. The equipment performance
m e a s u r e s indicated do not restore normal
checklist provides a procedure for systemati-
equipment performance, trouble-shooting is re-
cally checking equipment performance. All the
quired by higher category. Note on the repair
corrective measures that the repairman can per-
tag how the equipment performed and the cor-
form are given in the Corrective measures col-
rective measures that were taken.
b. Checklist.
Note: Perform the following with the polarity switch set to + (positive).
Caution: Do not rock or rotate a tube when
3-12. Replacement of Fuse
removing it from its socket: use a tube puller
If the vtvm is completely inoperative, the
and pull the tube straight out.
fuse is probably defective. Replace the defec-
a. General. Before replacing any- tubes,
tive fuse with a new one. If the new fuse
blows when power is applied, higher level re-
check the power cord and fuses as the possible
pair is required. Replace the fuse as follows:
source of trouble. If the trouble is not found,
follow the instructions given in b and c below
counterclockwise to unlock the cap.
to check the tubes.
b. Use of Tube Tester. Remove the two se-
fective fuse.
curing screws at the rear of the vtvm and pull
c. Remove the defective fuse and replace it
the chassis out of the case. Remove and test
with a new one.
one tube at a time. Discard a tube only if a
defect is obvious or the tube tester shows it to
Note: A l-ampere fuse (cartridge type) is required
for 115-volt operation; a -ampere fuse (cartridge
be defective. Do not discard a tube that tests
type) is required for 230-volt operation.
at or near its minimum test limit. Replace the
original tube, or insert a new one of required.
3-13. Replacement of Tubes
before testing the next one.
c. Tube Substitution Method. Replace a
Warning: Tube OA2/WA contains radioac-
suspected tube with a new tube. If the equip-
tive material. Handle carefully to avoid
ment still does not work, remove the new tube
breaking.
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