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.

Pages 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12

MIL-PRF-39035E

3.5.11 Solder dip (retinning) leads (not applicable to terminal L). The manufacturer (or his authorized category B

or C distributor) may solder dip/retin the leads of product supplied to this specification provided the solder dip process

(see appendix A) has been approved by the qualifying activity.

3.5.11.1 Welding and brazing. Where welding and brazing is employed, the electrical connections shall be

mechanically secure and electrically continuous after welding and brazing. Where brazing is employed only,

substantially noncorrosive fluxes shall be used, unless it can be shown that corrosive elements have been

satisfactorily removed after brazing.

3.6 Power rating. The resistors shall have a power rating based on continuous full-load operation at the ambient

temperature specified (see 3.1 and figure 2). The power rating is dependent on the ability of the resistors to meet the

life requirements specified in 3.30. For temperatures in excess of those specified, the load shall be derated as shown

on figure 2. Power ratings as specified (see 3.1), are applicable only when the maximum resistance is engaged in the

circuit. The power rating is reduced in approximately the same proportion as the resistance.

100

120

140

160

180

150

AMBIENT TEMPERATURE IN C

FIGURE 2. Derating curve for high-ambient temperatures.

3.7 Voltage rating. The theoretically calculated rated continuous working voltage or the voltage equivalent to

power rating (rated wattage) shall be determined from the following formula:

E = PR

Where:

E = Rated dc or rms ac continuous working voltage at commercial-line frequency and waveform.

P = Power rating (see 3.1).

R = Nominal resistance (see 3.1).

In no case shall the rated dc or rms continuous working voltage be greater than the applicable maximum value

3.8 Conditioning. When resistors are tested as specified in 4.8.2, there shall be no mechanical damage. The

change in total resistance shall not exceed �2 percent for characteristic C, �1.5 percent for characteristic F, and �1

percent for characteristic H.