MIL-PRF-39035 Resistor, Variable, Nonwirewound \(Adjustment Type\), Nonestablished Reliability, And Established Reliability, General Specification ForThis specification covers the general requirements for nonestablished reliability \(non-ER\) and established reliability \(ER\), multiturn lead-screw actuated, and single-turn, nonwirewound, variable resistors with a contact bearing uniformly over the surface of the entire resistive element, when positioned by an actuator. These resistors are capable of full-load operation \(when the maximum resistance is engaged\), at a maximum temperature of 150 Degrees C, with a resistance tolerance of ??10 percent. The ER resistors will have life failure rate levels ranging from 1.0 to 0.001 percent per 1,000 hours \(see 1.2.1.5\). These failure rate levels are established at a 60 percent confidence level maintained at 10 percent producer\'s risk on the basis of the life tests.

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MIL-PRF-39035E

3.27 High temperature exposure. When tested as specified in 4.8.22, resistors shall meet the following requirements:

Change shall not exceed �2 percent.

Setting stability:

Change shall not exceed �3 percent.

Total resistance:

As specified in 3.14. (atmospheric pressure).

Dielectric withstanding voltage:

Insulation resistance:

Shall not be less than 1,000 megohms.

Visual examination:

There shall be no evidence of mechanical damage.

3.28 Rotational life. When the resistors are tested as specified in 4.8.23, the change in total resistance shall not

exceed �2 percent, and there shall be no mechanical damage. The failure of one pair of units being tested shall not

count as a failure for the companion unit.

3.29 Terminal strength. When the resistors are tested as specified in 4.8.24, there shall be no evidence of

mechanical damage, and resistors shall be electrically continuous.

3.30 Life.

3.30.1 Qualification. When the resistors are tested as specified in 4.8.25, there shall be no evidence of mechanical

damage. The change in resistance between the initial measurement and any of the succeeding measurements shall

not exceed �3 percent.

3.30.2 Failure-rate level determination. When the resistors are tested as specified in 4.8.25, there shall be no

evidence of mechanical damage to the resistance element, or enclosure. The change in resistance between the initial

measurement and any of the succeeding measurements shall not exceed �5 percent. This single failure criteria shall be

applicable to all measurements during the life test for purposes of determining failure rate level qualification and is

applicable as a parallel requirement with 3.30.1 to the measurements made during the life test specified for the

qualification inspection.

3.31 Resistance to solvents. When the resistors are tested as specified in 4.8.26, there shall be no evidence of

mechanical damage and the markings shall remain legible.

3.32 Low temperature storage (qualification only). When the resistors are tested as specified in 4.8.27, the change in

total resistance shall not exceed �2 percent for characteristic C, and �1 percent for characteristics F and H.

3.33 Marking.

3.33.1 Full marking. The resistors shall be marked with the PIN (see 3.1), and "JAN" brand. In addition, the

resistor shall be dated and source coded in accordance with MIL-STD-1285. Where the date coding does not provide

specific lot identification, the manufacturer shall mark the resistor with the lot code symbol. Where required, the PIN

may appear on two lines as shown in the following example:

RJR24F

P102M

Marking shall remain legible at the end of all tests.