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

4.6 Conformance inspection.

4.6.1 Inspection of product for delivery.

4.6.1.1 Non-ER resistors. Inspection of product for delivery shall consist of the requirements in 4.6.3.1.

4.6.1.2 ER resistors. Inspection of product for delivery shall consist of group A inspection.

4.6.2 Inspection and production lot.

4.6.2.1 Inspection lot. An inspection lot as far as practicable, shall consist of all resistors of the same style,

characteristic, and protective enclosure or coating and manufacturer under essentially the same process and

conditions during a manufacturing period of 1 month maximum. For purposes of lot formation all terminal types may

be included in the same lot; however, all lead types which are combined shall have the same method of terminal

attachment. All leads in the lot shall be represented in a similar proportion by samples selected for inspection. Non-

ER and ER lots shall be kept separate.

4.6.2.2 Production lot. A production lot shall consist of resistors of the same characteristic, style, nominal

resistance value, resistance tolerance, and terminal style. Manufacture of all parts in the lot shall have been started,

processed, assembled, and tested as a group. Lot identity shall be maintained through the manufacturing cycle.

Non-ER and ER lots shall be kept separate.

4.6.3 Group A inspection.

4.6.3.1 Non-ER resistors. The manufacturer shall establish and maintain an inspection system to verify resistors

meet visual/mechanical, contact resistance variation, total resistance, immersion, and solderability requirements.

In-line or process control may be part of such a system. The inspection system shall also include criteria for lot

rejection and corrective actions. The inspection system shall be verified under the overall MIL-STD-790 QPL system.

NOTE: Since the non-ER (C level) is the ER design without the mandatory conformance inspection and FR level

assessment, this product is still expected to meet the environmental qualification type requirements

(e.g., moisture resistance, shock, vibration, etc.)

4.6.3.2 ER resistors. Group A inspection shall consist of the inspections specified in table VII, in the order shown.

4.6.3.2.1 Subgroup 1 tests. Subgroup 1 tests shall be performed on a production lot basis on 100 percent of the

product supplied under this specification. Resistors that are out of resistance tolerance, or which experience a

change in resistance greater than that permitted for the tests of this subgroup shall be removed from the lot. Only lots

having not more than 10-percent rejects or one resistor, whichever is greater due to exceeding the specified

resistance change limit, as a result of subgroup 1 tests shall not be furnished on orders. Corrective action shall be

taken on such values and new pieces furnished.