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

Final measurements: Upon completion of step 6 of the final cycle, the resistors shall be removed from the

chamber and air dried for one-half hour at room ambient conditions. Samples shall not be subjected to

forced air drying. The total resistance and insulation resistance shall then be measured as specified in

4.8.5.1 and 4.8.9, respectively. The subsequent 24-hour conditioning period and measurements do not

apply.

Examination after test: Resistors shall be examined for evidence of mechanical damage.

Steps 7A and 7B: Steps 7A and 7B are not applicable to this specification.

4.8.16 Setability (see 3.21). The resistor wiper shall be set at approximately 30 percent, 50 percent, and 75

percent of mechanical rotation. A dc voltage of up to 2.5 volts shall be applied across the end terminals, and the

wiper shall then be adjusted smoothly without abrupt voltage change at each test point. The setability error shall be

within the limits specified.

4.8.17 Shock (specified pulse) (see 3.22). Resistors shall be tested in accordance with method 213 of

MIL-STD-202. The following details and exceptions shall apply:

Mounting: Resistors shall be mounted by their normal mounting means, with their bodies restrained from

movement, on an appropriate mounting fixture.

Test leads: Test leads used during this test shall be no larger than AWG size 22 stranded wire, so that

the influence of the test lead on the resistor will be held to a minimum. The test lead length shall be no

longer than necessary.

Measurements before shock: Total resistance and setting stability shall be measured as specified in

Test condition: I.

Measurements during shock: Each resistor shall be monitored to determine electrical discontinuity of the

resistance element, and between the contact arm and element, by a method that shall at least be sensitive

enough to monitor or register, automatically, any electrical discontinuity of 0.1 millisecond or greater

duration.

Measurements after shock: Setting stability and total resistance shall be measured as specified in 4.8.12

and 4.8.5.1, respectively.

Examination after shock: Resistors shall be examined for evidence of mechanical damage.

4.8.18 Vibration, high frequency (see 3.23). Resistors shall be tested in accordance with method 204 of

MIL-STD-202. The following details and exceptions shall apply:

Mounting: As specified in 4.8.17a.

Test leads: As specified in 4.8.17b.

Measurements before vibration: As specified in 4.8.17c.

Test condition: D.