MIL-R-93 Resistors, Fixed, Wire-Wound, Accurate, General Specification ForThis specification covers the general requirements for accurate, wire-wound, fixed resistors having a maximum resistance tolerance of 1 percent, with the winding protected against high humidity. The resistors are rated for continuous full load operation at any ambient temperature up to 125 Degrees C, and derated up to 145 Degrees C. They are not capable for application where alternating current ac characteristics are of critical importance. Performance characteristics are in accordance with table I.

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MIL-R-93F

4.7.3 Short time overload (see 3.7). DC resistance shall be measured as specified in 4.7.2. Each resistor shall be subjected to a dc test potential equivalent to that calculated for twice the rated wattage, but not to exceed twice the maximum voltage (see 3.1), for 10 minutes under the following conditions:

a. In free space, predicated on horizontal mounting with the resistor mounted in a minimum of 0.5 inch (12.7 mm) from any other resistor or the mounting base.

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.

4.7.4 Thermal shock (see 3.8). Resistors shall be tested in accordance with method 107 of

MIL-STD-202 . The following details and exceptions shall apply:

a. Mounting: In such a manner as to present a minimum obstruction to the airstream. In no case shall the fixture prevent the specified ambient temperature from being achieved within 4 minutes after the resistors are placed in the chamber.

b. Measurement before cycling: DC resistance shall be measured as specified in 4.7.2. c. Test condition: B.

d. Measurement after cycling: Not less than 1 hour, but within a 24 hour period after the last cycle, dc resistance shall be measured as specified in 4.7.2.

e. Examination after test: Resistors shall be examined for evidence of mechanical damage.

4.7.5 Solderability (see 3.9). Resistors shall be tested in accordance with method 208 of

MIL-STD-202 . The following detail shall apply: Both terminals shall be tested. The terminals shall be dipped within 0.0625 inch of the body.

4.7.6 Resistance to solvent. (see 3.10). Resistors shall be tested in accordance with method 215 of

MIL-STD-202 . The following details shall apply:

a. The marked portion of the resistor body shall be brushed.

b. The number of sample units shall be as specified in table VII.

c. Resistors shall be examined for mechanical damage and legibility of markings.