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

4.4.4 FR qualification (ER only). FR qualification shall be in accordance with the general and detail

requirements of MIL-STD-690 and the following details:

a. Procedure I: Qualification at the initial FRL. Level M (1.0 percent) of FRSP-60 shall apply.

Sample units shall be subjected to the qualification inspection specified in group VI, table IX (see

4.4.2). Entire life test sample shall continue on test to 10,000 hours as specified in 4.8.17, upon

completion of the 2,000 hour qualification.

b. Procedure II: Extension of qualification to lower FRL. To extend qualification to the R (0.01

percent) and S (0.001 percent) FRL s, data from two or more styles of similar construction may be

combined.

c. Procedure III: Maintenance of FRL qualification. Maintenance period A of FRSP-10 of

MIL-STD-690 shall apply. Regardless of the number of production lots produced during this

period, the specified number of unit hours shall be accumulated to maintain qualification (see

4.7.1, group C inspection).

4.5 Verification of qualification. Every six months, the manufacturer shall provide verification of

qualification to the qualifying activity. Continuation of qualification is based on meeting the following

requirements:

b. The manufacturer has not modified the design of the item.

c. The specification requirements for the item have not been amended so far as to affect the

character of the item.

d. Lot rejection for group A inspection does not exceed 15 percent or one lot, whichever is greater.

e. Lot rejection for group B inspection does not exceed 5 percent or one lot, whichever is greater.

(Subgroup 2, group B, not included in reject rate).

f. The requirements for group C inspection are met.

g. The records of FR tests combined substantiate that the "M" (1.0 percent), or "P" (0.1 percent) FRL

has been maintained, or that the manufacturer continues to meet the "R" (0.01 percent), and "S"

(0.001 percent) FRL for which qualified, although the total component hours of testing does not, as

yet, meet the requirements of 4.4.4c.

h. Continued qualification to the non-ER level (C) shall be based on continued maintenance of

qualification for the ER part (minimum "P" FRL maintenance).