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

3.19 Resistance-temperature characteristic. When resistors are tested as specified in 4.8.14, the resistance-

temperature characteristics shall be referred to an ambient temperature of 25OC. Resistors shall not exceed the

applicable values specified in table I.

3.20 Moisture resistance. When resistors are tested as specified in 4.8.15, resistors shall meet the following

requirements:

Change shall not exceed �2 percent for characteristic C, and �1 percent for

Total resistance:

characteristics F and H.

Insulation resistance:

Shall not be less than 100 megohms.

Visual examination:

There shall be no evidence of mechanical

3.21 Setability. When resistors are tested as specified in 4.8.16, the setability shall be �1 percent maximum.

3.22 Shock (specified pulse). When resistors are tested as specified in 4.8.17, the change in total resistance shall

not exceed �1 percent. The change in setting stability shall not exceed �1 percent. There shall be no electrical

discontinuity or evidence of mechanical damage.

3.23 Vibration, high frequency. When resistors are tested as specified in 4.8.18, there shall be no electrical

discontinuity, and resistors shall meet the following requirements:

Change shall not exceed �1 percent.

Setting stability:

Change shall not exceed �1 percent.

Total resistance:

Visual examination:

There shall be no evidence of mechanical damage.

3.24 Salt spray (corrosion). When resistors are tested as specified in 4.8.19, there shall be no appreciable

corrosion which will affect the life or serviceability. If the base metal is corroded, it shall be considered a defect.

3.25 Resistance to soldering heat. When resistors are tested as specified in 4.8.20, the change in total resistance

shall not exceed �1 percent. There shall be no evidence of mechanical damage.

3.26 Low temperature operation. When resistors are tested as specified 4.8.21, resistors shall meet the following

requirements:

Change shall not exceed �2 percent.

Setting stability:

Change shall not exceed �2 percent for characteristic C, and �1 percent for

Total resistance:

characteristics F and H.

Visual examination:

There shall be no evidence of mechanical damage.