MIL-R-10509J
4.7.4 Thermal shock (see 3.9). Resistors shall be tested in accordance with method 107 of
MIL-STD-202. The following details and exception shall apply:
a. Mounting: Resistors shall be mounted by means other than soldering.
b. Measurements before cycling: DC resistance shall be measured as specified in 4.7.2. c. Test condition letter: F.
d. Measurement after cycling: Within 3 hours after completion of the final cycle and as soon as the resistors stabilize at room temperature, dc resistance shall again be measured as specified in
4.7.2.
Following the test, resistors shall be examined for evidence of mechanical damage.
4.7.5 Low temperature operation (see 3.10).
4.7.5.1 Mounting. Resistors shall be mounted by their terminals so that there is at least 1 inch (2.54 mm) of free air space around each resistor and the mounting is in such a position with respect to the air that it offers substantially no obstruction to the flow of air across and around the resistors.
4.7.5.2 Procedure. Following the final dc resistance measurement specified in 4.7.4d, the resistors mounted as specified in 4.7.5.1, shall be placed in a cold chamber at room temperature. The temperature shall be gradually decreased to -65°C +0°C, -5°C, within a period of not less than 1.5 hours. For conformance inspection only, and at the option of the manufacturer, the resistors may be placed in the cold chamber when the chamber is already at the extreme low temperature. After 1 hour of
stabilization at this temperature, full rated continuous working voltage as specified 3.6 shall be applied for
45 minutes. The resistors may be loaded individually or in parallel. Fifteen minutes +5 minutes, -0 minutes after the removal of the voltage, the temperature in the chamber shall be gradually increased to room temperature within a period of not more than 8 hours. The resistors shall be removed from the chamber and maintained at a temperature of 25°C ±5°C for a period of approximately 24 hours; the dc resistance shall then be measured as specified in 4.7.2. Resistors shall then be examined for evidence of mechanical damage.
4.7.6 Short time overload (see 3.11). DC resistance shall be measured as specified in 4.7.2. A dc test potential, 2.5 times the rated continuous working voltage but not exceeding twice the maximum voltage specified (see 3.1), shall then be applied for 5 seconds to the resistor terminals under the following conditions:
a. In free space, mounted horizontally, with no circulation other than that created by the heat of the resistors being operated.
b. In still air, with no circulation other than that created by the heat of the resistors being operated. Thirty minutes +15 minutes, -0 minutes after removal of the test potential, the dc resistance shall again be
measured as specified in 4.7.2. Resistors shall then be examined for evidence of arcing, burning, and
charring.
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