MIL-PRF-39005 Resistors, Fixed, Wirewound \(Accurate\), Nonestablished Reliability, Established Reliability, General Specification ForThis specification covers the general requirements for nonestablished reliability \(non-ER\), established reliability \(ER\), accurate, wire-wound, fixed resistors that have a maximum resistance tolerance of 1 percent and a high degree of stability with respect to time under specified environmental conditions. The resistors are capable for continuous full-load \(or voltage\) operation at any ambient temperature up to 125??C, and when derated, up to 145??C \(see 6.5\). They are not capable for application where the alternating current \(ac\) characteristics are of critical importance. ER resistors have life failure rates \(FR\) ranging from 1.0 percent to 0.001 percent per 1,000 hours \(see 1.2.1.5\). These FR are established at 60-percent confidence level on the basis of the life tests. The FR, identified by the appropriate symbol, is referred to operation at full rated voltage and temperature.

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MIL-PRF-39005G

f. Measurements during test:

(1) Qualification inspection: DC resistance shall be measured at the end of the 30 minutes "off"

periods after 250 hours +72 hours, -24 hours; 500 hours +72 hours, -24 hours; 1,000 hours

+72 hours, -24 hours; and 2,000 hours +96 hours, -24 hours have elapsed.

(2) Extended life testing: DC resistance shall be measured at the end of the 30 minute "off"

periods after 250 hours +72 hours, -24 hours; 500 hours +72 hours, -24 hours; 1,000 hours

+72 hours, -24 hours; 2,000 hours +96 hours, -24 hours; 4,000 hours +96 hours, -24 hours;

6,000 hours +96 hours, -24 hours; 8,000 hours +96 hours, -24 hours; and 10,000 hours +120

hours, -0 hour have elapsed. Measurements shall be made as near as possible to the

specified time but may be adjusted so that measurements need not be made during other than

normal work days.

(3) Measurement outside chamber: When measurements are made outside the chamber,

resistors shall be outside the chamber for a minimum of 45 minutes and stabilized before

measurements.

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

4.8.18 Fungus (see 3.22). Resistors shall be tested in accordance with method 508 of MIL-STD-810.

Resistors shall be examined for evidence of fungus.

4.8.19 Resistance to solvents (see 3.23). 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 IX and table XIII, as applicable.

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

4.8.20 High temperature exposure (see 3.24).

a. Mounting: Resistors shall be mounted by their normal mounting means.

b. Initial measurements: DC resistance shall be measured as specified in 4.8.5 at room ambient

conditions.

c. Procedure: Following initial resistance measurements resistors shall be placed in a chamber

maintained at 145�C �5�C for a period of 2,000 hours with no load applied.

d. Measurements during test: At 250 hours +48 hours, -0 hours, resistors shall be removed from the

chamber and permitted to stabilized at room temperature and within 6 hours after removal, the dc

resistance shall be measured as specified in 4.8.5. Resistors shall be examined for evidence of

mechanical damage.

e. Final measurements: After removal from test chamber, resistors shall be permitted to stabilize at

room ambient temperature, and within 6 hours after removal, cleaning of the leads will be allowed.

The dc resistance shall be measured as specified in 4.8.5. Resistors shall be examined for

evidence of mechanical damage.