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

4.4.4 FR qualification. FR qualification shall be in accordance with the general and detail requirements of

MIL-STD-690 and the following details:

Procedure I - Qualification at the initial FR level. Level M (1.0 percent) of FRSP-60 shall apply. Sample

units shall be subjected to the qualification inspection specified in group VII of table VI (see 4.4.2). Entire

life test sample shall continue on test to 10,000 hours as specified in 4.8.25, upon completion of the 2,000

hour qualification.

Procedure II - Extension of qualification to lower FR levels. To extend qualification to the R level (0.01

percent) and S (0.001 percent) FR levels, unit hours from two or more styles of similar construction may

be combined.

Procedure III - Maintenance of FR level qualification. Maintenance period B of FRSP-10 shall apply.

Regardless of the number of production lots produced during this period, the specified number of unit

hours shall be accumulated to maintain qualification (see 4.7.2.1). For FR levels M, P, R, and S unit hours

from all lead types may be combined.

4.4.5 PPM level verification. The contractor is responsible for establishing a quality system to assess the ppm

level of lots that are subjected to group A inspections. The ppm defect level shall be based on a 6-month average.

4.5 Verification of qualification. Every 6 months, the manufacturer shall provide verification of qualification to the

qualifying activity. Continued qualification is based on meeting the following requirements.

Design of resistor has not been modified.

Lot rejection for group A (subgroup 1 and subgroup 3) does not exceed 10 percent or one lot, whichever is

greater.

Periodic group B inspection.

FR levels.

PPM assessment (NOTE: Grouping of style is permitted).

Continued qualification to non-ER (C) shall be based on continued maintenance of qualification for the ER

part (minimum "M" FR level maintained).