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

3.35 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or

environmentally preferred materials should be used to the maximum extent possible provided that the

materials meets or exceeds the operational and maintenance requirements, and promotes economically

advantageous life cycle costs.

3.36 Workmanship. Resistors shall be processed in such a manner as to be uniform in quality and

shall be free any defects that will affect life, serviceability or appearance.

4. VERIFICATION

4.1 Classification of inspections. The inspection requirements specified herein are classified as

follows:

a. Qualification inspection (see 4.4).

b. Verification of qualification (see 4.5).

Conformance inspection (see 4.6).

d. Periodic group C inspection (see 4.7).

4.2 Reliability and quality.

4.2.1 QPL system. The manufacturer shall establish and maintain a QPL system in accordance with

3.3. Evidence of such compliance is a prerequisite for qualification and retention of qualification.

4.2.2 SPC. A SPC program shall be establish and maintained in accordance with EIA-557. Evidence

of such compliance shall be a prerequisite for qualification and verification of qualification.

4.3 Inspection conditions and precautions.

4.3.1 Inspection conditions. Unless otherwise specified herein, all inspections shall be performed in

accordance with the test conditions specified in the "GENERAL REQUIREMENTS" OF MIL-STD-202.

4.3.2 Precautions. Adequate precautions shall be taken during inspection to prevent condensation of

moisture on resistors, except during moisture resistance test. Precautions shall be taken to prevent

damage by heat when soldering resistor leads to terminals.

4.4 Qualification inspection. Qualification inspection shall be performed at a laboratory acceptable to

the Government (see 6.3), on sample units produced with equipment and procedures normally used in

production.

4.4.1 Sample. The number of sample units comprising a sample of resistors to be submitted for

qualification inspection shall be as specified in the appendix A to this specification. The sample shall be

taken at random from a production run and shall be produced with equipment and procedures normally

used in production.