MIL-R-19365E
6.6 Supplementary insulation. When voltages greater than 500 volts dc, or 350 volts ac rms, are present between resistor circuits and grounded surfaces on which resistors are mounted, supplementary insulation capable of withstanding the voltage condition should be provided between resistors and mountings and ground.
6.7 Mounting. Resistor should not be mounted by their terminals.
6.7.1 Bracket assemblies. When required (see 6.2), bracket assemblies (mounting hardware) are available for these resistors under MS75009, Bracket Assembly, Resistor (Power Type).
6.8 Choice of styles. The styles of resistors to be used in equipment should be so chosen that, when mounted in the equipment, they will not be required to operate at a temperature in excess of their rating. This should be applicable under the most severe combination of conditions with the equipment operating as follows:
a. In the maximum specified ambient temperature.
b. Under conditions producing maximum temperature rise in each resistor.
c. For a sufficient length of time to produce maximum temperature rise, or for the maximum specified time. d. With all enclosures in place.
e. With natural ventilation only (this should permit the use of any special ventilating provisions included as a standard part of the equipment).
f. At high altitude.
6.9 Soldering. When operated at full load, the maximum temperature may be 3500C. The solder used for connecting leads to the terminals should be chosen accordingly.
6.10 High frequency. Resistors should not be used in circuits where their ac performance is of critical importance in the operation of such circuits.
6.11 Adjustments. Lugs should always be loosened completely before moving and should not be except while the voltage is off, in order to protect the operator from dangerous voltages. When adjusted to the position desired, the adjustable terminal should be tightened sufficiently to assure good electrical contact.
6.12 Tin whisker growth. The use of alloys with tin content greater than 97 percent, by mass, may exhibit tin whisker growth problems after manufacture. Tin whiskers may occur anytime from a day to years after manufacture and can develop under typical operating conditions, on products that use such materials. Conformal coatings applied over top of a whisker-prone surface will not prevent the formation of tin whiskers. Alloys of 3 percent lead, by mass, have shown to inhibit the growth of tin whiskers. For additional information on this matter, refer to ASTM-B545 (Standard Specification for Electrodeposited Coatings of Tin).
6.13 Subject term (key word) listing.
Bracket assemblies
High frequency
Hotspot surface temperature
6.14 Environmentally preferable material. Environmentally preferable materials should be used to the maximum extent possible to meet the requirements of this specification. As of the dating of this document, the U.S. Environmentally Protection Agency (EPA) is focusing efforts on reducing 31 priority chemicals. The list of chemicals is available on their website at https://www.epa.gov/epaoswer/hazwaste/minimize/chemlist.htm. Further information is available at the following EPA site: https://www.epa.gov/epaoswer/hazwaste/minimize/. Included in the EPA list of 31 priority chemicals are cadmium, lead, and mercury. Use of the materials on the list should be minimized or
eliminated unless needed to meet the requirements specified herein (see Section 3).
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