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.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12

MIL-PRF-39035E

4.8.8 Dielectric withstanding voltage (see 3.14).

4.8.8.1 Atmospheric pressure. The resistors shall be tested in accordance with method 301 of MIL-STD-202. The

following details shall apply:

Special preparations: The resistors shall be mounted on metal plates of sufficient size to extend beyond

the resistor extremities, and in such a manner that measurements can be made between the terminals tied

together and any other external metal parts.

Magnitude of test voltage: As specified in 3.1.

Nature of potential: From an alternating-current (ac) supply at commercial-line frequency and waveform.

This potential shall be applied for 1 minute.

Points of application of test voltage: Between the terminals connected together and all external metal

portions of the resistors and metal-mounting plate.

Examinations and measurements: During the tests, the leakage current shall be monitored and the

resistors examined for evidence of arcing and breakdown. At the conclusion of the test, resistors shall be

examined for evidence of damage.

4.8.8.2 Barometric pressure. Resistors shall be tested in accordance with method 105 of MIL-STD-202. The

following details and exceptions shall apply:

Method of mounting: As specified in 4.8.8.1a.

Test condition: C.

Period of time at reduced pressure prior to application of potential: 1 minute.

Test during subjection to reduced pressure: Voltage as specified (see 3.1) from an ac supply at

commercial line frequency and waveform shall be applied for 1 minute.

Points of application: As specified in 4.8.8.1d.

Examinations and measurements: As specified in 4.8.8.1e.

4.8.9 Insulation resistance (see 3.15). Resistors shall be tested in accordance with method 302 of MIL-STD-202.

The following details shall apply:

Test condition: A or B, whichever is more practicable.

Special preparation: As specified in 4.8.8.1a.

Points of measurement: As specified in 4.8.8.1d.

4.8.10 Torque.

4.8.10.1 Operating (see 3.16.1). The torque required to move the contact arm on the resistance element shall be

determined at approximately 10 percent, 50 percent, and 90 percent of actual effective-electrical travel by the

torque-wrench method or by any other method approved by the Qualifying Activity.