Service manual

STP 11-25R13-SM-TG
T - 6
g. Knives, screwdrivers, or other thin-edged tools will not be used to remove vacuum tubes. Tube
pullers will be used for hard-to-remove tubes.
h. Fuse pullers are used to remove or replace fuses, except for removable fuseholders that are
designed to remove by hand. Fuses will not be replaced while power is applied to the circuit. The circuit
must be completely deenergized. Metal substitutes or higher-rated fuses will not be used to replace
expended, burned-out fuses. A slow-blow fuse will not be used to replace a fuse of the fast-blow variety
and vice versa. Whenever practical, a circuit should be checked before replacing a burned-out fuse as
the trouble is often indicative of a circuit fault.
i. Nonconductive alignment tools will be used. All other hand tools used in or around
electrical/electronic circuits will have insulated handles when practical.
j. Soldering irons will be turned off when left unattended or will be placed in covered holders. Be
very careful when soldering or unsoldering wires or components under tension. Eyes must be shielded
(safety glasses, goggles, etc.) while soldering or unsoldering to prevent molten solder from staking the
eyes when wires or components break loose. Silver solder containing cadmium will not be used. If no
substitute is effective, a waiver must be obtained, adequate ventilation and other industrial hygiene
controls must be provided, and the workers should be included in a medical surveillance program to
prevent the toxic effects of inhaled cadmium fumes.
k. Where dangerous voltages exist, flooring and work surfaces will be of non-conductive material
meeting the requirements of MIL-M-15562 (i.e., safety rubber or vinyl matting). See GSA Supply Catalog,
Industrial Products, for types, sizes, colors, etc., which are available. Nonconductive safety shoes may
be provided as an additional safety measure. (Safety shoes will be tested before being issued to be sure
they are nonconductive.) The minimum allowable resistance under maximum working voltage for a given
area will be not less than 1 megohm per kilovolt when tested in accordance with procedures of (1) and (2)
below. Where the minimum resistance level is not reached, additional insulation (rubber mats, wooden
platforms, etc.) will be provided to sufficiently increase the actual resistance to the above acceptable
level.
(1) Initial tests (Figure T-1) shall be made of all nonconductive floorings and work surfaces for the
minimum allowable resistance as specified above. Subsequent tests shall be made at least annually.
Coordination with the facility engineer may be required during testing. Records will be prepared,
identifying pertinent data and corrective actions taken, to assure the adequacy of flooring and work
surfaces. This record will be kept on file locally for at least 2 years and then destroyed.
(2) For the purpose of this bulletin, the term nonconductive is used to define the ability of a material
to withstand a voltage potential with little or no current flow through the material to be tested. A high
resistance measurement instrument (ZM-21/U Megger, or equivalent) with a minimum output of 500 volts
shall be used. One electrode of the measurement instrument should be firmly connected to a 5-pound
metal block, which has a contact surface of 5 square inches of good conducting material. The block
should be equipped with a nonconductive strap to pull it along the surface under test. The entire surface
of the nonconductive floorings, or work surfaces, shall be tested to determine the points of lowest
resistance to assure compliance with these requirements.