MIL-PRF-26H
(a) Tab-terminal, tubular resistors: Mounted as specified in 4.7.8.1a.(2).
(b) Axial terminal resistors: Mounted with V-shaped metal straps as specified in 4.7.11a.(3).
(c) All others mounted as specified in 4.7.11a.
(2) Loading voltage: During the first 2 hours of steps 1 and 4, a dc potential equivalent to 85 percent of
rated wattage, shall be applied between the terminals of each resistor. The negative terminal shall be
electrically grounded. This procedure is applicable to four of the sample units mounted as follows:
(a) Tab-terminal tubular resistors mounted with supplementary insulation as specified in 4.7.11a.(2).
(b) Axial terminal resistors mounted without V-shaped metal straps as specified in 4.7.11a.(3).
(c) All others mounted as specified in 4.7.11a.
(d) Subcycle: Step 7b shall not be applicable. Step 7a shall be performed during any five of the first
nine cycles only.
(e) Final measurements: On completion of step 6 of the final cycle, the resistors shall be held at the
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high-humidity condition and a temperature of 25 C ±2 C for a period of 1.5 hours to 3.5 hours.
The same straps used for polarizing the resistors may also be used for the insulation resistance
tests. To perform these tests, the resistors shall be removed from the chamber and within .5 hour
the insulation resistance, and dc measurement tests shall be performed as specified in 4.7.9 and
4.7.2, respectively.
(f)
Inspection after test: Resistors shall be inspected for evidence of mechanical damage.
4.7.12 Low-temperature storage (see 3.16).
4.7.12.1 Mounting. Resistors shall be mounted by their normal mounting means and in such a manner that there
is at least 1 inch of free air space around each resistor, and in such a position with respect to the air stream that the
mounting offers substantially no obstruction to the flow of air across and around the resistors.
4.7.12.2 Procedure. DC resistance shall be measured as specified in 4.7.2. Within 1 hour after this measurement,
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the resistors shall be placed in a cold chamber at a temperature of -65 C ±2 C for a period of 24 hours ±4 hours.
The resistors shall then be removed from the chamber and maintained at a temperature of 25OC ±5OC for a period of
approximately from 2 hours to 8 hours; the dc resistance shall again be measured as specified in 4.7.2. Resistors
shall then be examined for evidence of mechanical damage.
4.7.13 Mechanical strength (not applicable to axial-terminal resistors). Resistors shall be supported .125 inch
(3.18 mm) from each end. All except tab-terminal, stack-mounting resistors shall then be subjected to a transverse
load of not less than 50 pounds; tab-terminal, stack-mounting resistors shall be subjected to a load of 25 pounds. For
all except tab-terminal, stack-mounting resistors, the load shall be applied at the center of the resistor through a
fulcrum having a radius of not less than .25 inch (3.2 mm); for tab-terminal, stack-mounting resistors the load shall be
applied normal to the wide surface of the resistor (see 3.17).
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