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MIL-PRF-39015 Resistors, Variable, Wirewound, \(Lead Screw Actuated\), Nonestablished Reliability, And Established Reliability, General Specification ForThis specification covers the general requirements for nonestablished reliability \(non-ER\) and established reliability \(ER\), lead screw actuated; wirewound variable resistors with a contact bearing uniformly over the surface of the entire resistive element, wound linearly, when positioned by a multiturn lead screw actuator. These resistors are capable of full load operation \(when the maximum resistance is engaged\), at a maximum temperature of 85OC and are capable for continuous operation, when properly derated, at maximum temperature of 150OC \(see 3.6\), with a resistance tolerance of ??5 percent. The ER resistors have life failure rate \(FR\) levels ranging from 1.0 percent to 0.001 percent per 1,000 hours \(see 1.2.1.4\). These FR levels are established at a 60 percent confidence level on the basis of life tests.

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MIL-PRF-39015E

TABLE VI. Group A inspection.

Inspection

Requirement

Method

Sampling

paragraph

procedure

Subgroup 1 1/ 2/

4.8.2

3.8

Conditioning

100 percent

4.8.3

3.9

Peak noise

inspection

Total resistance 3/

Immersion

(not applicable to L terminals)

Subgroup 2

3.1, 3.3, to 3.3.2 incl., 3.4 to

Visual inspection 4/

See 4.6.3.2.3

3.5.8 incl., 3.33 and 3.34 incl.

Subgroup 3 5/ 6/

Continuity

Absolute minimum resistance

4.8.4.3

3.10.3

End resistance

See 4.6.3.2.4

4.8.7

3.13

Actual effective electrical travel

4.8.8

3.14

Dielectric withstanding voltage

4.8.9

3.15

Insulation resistance

Torque

Thermal shock

Subgroup 4

3.18

4.8.12

See 4.6.3.2.5

Solderability 5/ 7/

(applicable to terminals P, W, X, and Y)

1/ 100 percent solder dip may be performed prior to immersion (see A.5.3)

2/ At the manufacturer's option, the determination of resistance change may be by any method which

is within the accuracy requirements of this specification.

3/ Resistors shall meet this specified initial resistance tolerance. The resistance measurement made

upon completion of the conditioning test may be used if a measurement was made which can,

without conversion, be directly related to nominal resistance value and tolerance.

4/ The manufacturer may request the deletion of the subgroup 2 visual examination test, provided an

in-line or process control system for assessing and assuring the applicable requirements of the

visual examination test can be validated and approved by the qualifying activity. Deletion of the

test does not relieve the manufacturer from meeting this test requirement in case of dispute. If the

design, material, construction, or processing of the part is changed or if there are any quality

problems, the qualifying activity may require resumption of the test.

5/ At the option of the manufacturer, subgroup 2, subgroup 3, and subgroup 4 may be performed

concurrently with a separate set of samples.

6/ If the manufacturer can demonstrate that this test has been performed for 6 month with zero

failures, the frequency of this test, with the approval of the qualifying activity, can be performed on

an annual basis. If the design, material, construction, or processing of the part is changed, or if

there are any quality problems or failures, the qualifying activity may require resumption of the

original test frequency.

7/ The manufacturer may request the deletion of the subgroup 4 solderability test, provided an in-line

or process control system for assessing and assuring the solderability of leads can be validated

and approved by the qualifying activity. Deletion of the test does not relieve the manufacturer from

meeting this test requirement in case of dispute. If the design, material, construction, or processing

of the part is changed or if there are any quality problems, the qualifying activity may require

resumption of the test.