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

4.7.2 Monthly (subgroup 1). Samples shall be accumulated from each inspection lot and placed on

extended life test of 4.8.17 once a month for the full 10,000 hour life test. A sufficient number of samples

shall be selected from each lot by the manufacturer so that the maintenance of FR requirements is

complied with, within the specified maintenance period. In any event, a minimum of five samples shall be

selected from each lot. As far as practicable, the manufacturer shall select the resistance values so that

all resistance decades produced during the maintenance period are represented. The accumulated data

shall be used for maintenance or extension of FR qualification (see 3.21.2).

4.7.2.1 Monthly (subgroup 2). The 18 sample units of any resistance value shall be selected during the

two week period prior to the monthly testing specified in table XIV.

4.7.3 Quarterly. The 18 sample units of the highest resistance value shall be selected during the

month prior to the quarterly testing specified in table XIV.

4.7.4 Semiannually. The 6 sample units of any resistance value shall be selected during the month

prior to the semiannual testing specified in table XIV.

4.7.5 Annual. The 102 sample units shall be selected during the quarter prior to the annual testing

specified in table XIV.

4.7.5.1 Disposition of samples. Sample units which have been subjected to group C inspection shall

not be delivered on the contract.

4.7.6 Noncompliance. If a sample fails to pass group C inspection, the manufacturer shall notify the

qualifying activity and the cognizant inspection activity of such a failure and take corrective action on the

materials or processes, or both, as warranted, and on all units of production which can be corrected and

which were manufactured under essentially the same materials and processes, and which are considered

subject to the same failure. Acceptance and shipment of the product shall be discontinued until corrective

action, acceptable to the qualifying activity, has been taken. After the corrective action has been taken,

group C inspection shall be repeated on additional sample units (all inspections, or the inspection which

the original sample failed, at the option of the qualifying activity). Group A and group B inspections may

be reinstituted; however, final acceptance and shipment shall be withheld until the group C inspection has

shown that the corrective action was successful. In the event of failure after reinspection, information

concerning the failure shall be furnished to the cognizant inspection activity and the qualifying activity.

4.8 Methods of inspection.

4.8.1 Visual and mechanical inspection. Resistors shall be examined to verify that the materials,

design, construction, physical dimensions, marking and workmanship are in accordance with the

applicable requirements (see 3.1, 3.4, 3.5 to 3.5.6 inclusive, and 3.25, and 3.27 to 3.29 inclusive).