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MIL-PRF-19 Resistor, Variable, Wirewound \(Low Operating Temperature\), General Specification ForThis specification covers the general requirements for variable resistors having a resistance element of wirewound on an insulating strip shaped in an arc, so that a contract bears uniformly on the resistance element when adjusted by a control shaft. These resistors are capable of full load operation at an ambient temperature of +40 degrees C and are capable of continuous operation when properly derated, at a maximum temperature of +105 degrees C.

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MIL-PRF-19E

TABLE VII. Qualification inspection.

Examination

Requirements

Method

Number of

or test

paragraph

defectives 1/

Group I

Visual and mechanical

3.3 to 3.4.10 and

4.7.1

examination 2/

3.25 to 3.26 inclusive

Dielectric withstanding voltage

DC resistance

Torque

Group II

Low temperature storage

3.10

4.7.5

Low temperature operation

Thermal shock

Group III

Load life

3.13

4.7.8

Salt spray (corrosion)

3.14

4.7.9

Group IV

2 4/

Moisture resistance

3.15

4.7.10

Group V

Resistance to soldering heat

Rotational life

Switch life 3/

Insulation resistance

3.19

4.7.14

Group VI

Shock (specified pulse)

3.20

4.7.15

Vibration, high frequency

3.21

4.7.16

Group VII

Fungus

3.22

4.7.17

1/ Failure of an individual resistor in one or more tests of a test group shall be charged

as a single defective.

2/ Marking shall be considered defective only if it is illegible after completion of any of

the required inspections.

3/ Not applicable to locking bushing type resistors.

4/ Number of failures allowed in group III, IV, V, and VI is one, with a combined total of

two overall.