Service manual

STP 11-25R13-SM-TG
T - 5
work will stop until they have been discharged, unless otherwise specified in maintenance/repair
manuals.
(1) Conductors used to dissipate the charge on capacitors or capacitive circuits should contain
sufficient copper to dissipate the calculated maximum energy without excessive temperature rise, which
endangers soldered joints, etc. The length of the shorting bar must be ample for the reach and the
voltages involved. Connections made with a spring clip are not recommended.
(2) Shorting bar handles can be of rigid plastic or dry hardwood, painted with clear shellac. The
conductor must be bare, but transparent plastic tubing may be slipped over it. The end of the conductor
should terminate in a copper hook or clip so that it can be left hanging on a terminal of a discharged
capacitor during repair work as extra protection, since some of the charge may return due to a dielectric
affect.
c. Since cathode-ray tubes (CRTs) are subject to implosion, improper handling may result in
serious injury. Safety glasses with side shields, or other adequate protective eyewear, gloves, and apron
shall be worn at all times while handling CRTs. All high voltage terminals of CRTs will be shorted to
ground before handling.
d. Filaments on some high voltage vacuum rectifier tubes (such as 1B3-GT or 1V2) are capable of
producing a fatal shock if the filament circuits are not grounded.
e. Certain electron tubes contain radioactive materials. The required instructions for safe handling
and identification of these tubes are contained in TB 43-0116 and TB 43-0122. These tubes require
special handling to avoid contamination of personnel and surroundings in case of breakage. If breakage
occurs, use approved methods of monitoring, decontamination, and disposal. Under no condition will
unauthorized personnel handle broken or unbroken electron tubes containing radioactive material.
Broken and useless tubes containing radioactive material, such as spark gap, TR, glow lamp or cold
cathode tube, should be treated as any other radioactive waste material and disposed of in accordance
with instructions contained in AR 385-11. All tubes containing radioactive materials shall be identified
and marked in accordance with MIL-STD-1458. Unmarked tubes suspected of containing radioactive
materials should be checked with a beta-gamma sensing radiac instrument. When tests cannot be
conducted, or are indeterminate, all available data on tubes suspected of containing radioactive material,
but not listed in TB 43-0116 or TB 43-0122, should be submitted to COMMANDER, US ARMY
COMMUNICATIONS-ELECTRONICS COMMAND AND FORT MONMOUTH, ATTN: DRSEL-SF-H,
FORT MONMOUTH, NJ 07703, for evaluation. During the interim period, tubes that are suspect should
be stored in a safe and secure manner.
f. Selenium and cadmium fumes are highly toxic. Teflon/polyfluoride dielectric materials, which
may become overheated during soldering operations, will produce toxic fumes. Adequate ventilation and
other control measures must be provided, and precautions must be taken when heating cadmium-plated
objects. Toxic fumes, generated when cadmium-plated objects are overheated, must not be inhaled.
Individuals working with cadmium should be on a periodic medical surveillance program. Selenium
fumes have a very offensive odor similar to that of horseradish. The odor serves as adequate warning to
prevent illness from the fumes. When these odors are detected, the power to the affected instrument
must be turned off and the contaminated area evacuated immediately. Before personnel reenter the
contaminated area, it must be ventilated to remove the fumes. Overheated selenium rectifiers will not be
handled with bare hands. Skin contact with selenium compounds must be avoided. Properly located
placards with appropriate warning will be used in areas where toxic fumes are known to exist.