MIL-PRF-28776F
Contact rating (the highest dc resistive load rating shall be marked) (see 3.1).
h.
Circuit diagram (see 3.5.5).
i.
j.
3.28.3 Minimum marking (when specified, see 3.1). When space does not permit the marking specified in 3.28.2,
the marking shall include, as a minimum the military PIN; the "J" with the date code (example J8230); circuit diagram;
and manufacturer's name or source code.
3.28.4 Failure rate level substitution. With acquiring activity approval, relays qualified to lower (better) failure rates,
may be substituted for higher failure rate parts. For example, a relay qualified to failure rate level "P" (0.1
percent/10,000 cycles), may be substituted for a failure rate "M" (1.0 percent/10,000 cycles), relay. Unless specified
in the contract or purchase order, relays shall not be remarked.
3.28.5 Interchangeability. All parts having the same military PIN shall be directly and completely interchangeable
with each other with respect to installation and performance to the extent specified in the military specification sheet
(see 3.1).
3.29 Header glass. Header glass may have small irregularities, such as bubbles, chips, and cracks. The
acceptability shall be based on figure 2 and the following:
a.
Surface blisters whose diameters do not exceed one-half of the radial distance between the terminal and
the corresponding header metal (for a cluster of blisters, the overall cluster diameter shall apply) are
acceptable.
b.
Circumferential cracks which originate and terminate in the glass and which extend less than 135° are
acceptable (see figure 2, reference B).
c.
Radial cracks with lengths not exceeding three-quarters of the distance between the terminal and the
surrounding header metal are acceptable (see figure 2, reference C).
d.
Tangential cracks which are confined to a single zone are acceptable (see figure 2, reference D).
e.
Meniscus cracks, and chipouts, which completely surround the terminal are acceptable if:
(1)
The meniscus cracks, and chipouts do not extend beyond one-half the distance from the terminal to
the surrounding header metal, or
(2)
The meniscus cracks, and chipouts do not extend beyond one-quarter of the distance from the
terminal to the surrounding header metal and a portion of the meniscus cracks, and chipouts does not
extend beyond three-quarters of the distance from the terminal to the surrounding header metal if that
portion of the meniscus cracks, and chipouts does not span more the 180° (see figure 2, reference
E).
f.
An internal bubble whose diameter does not exceed one-third the distance between the terminal and the
surrounding header metal is acceptable.
Microscopic examination with up to 10X magnification shall be used. In case of dispute, all relays shall meet the
applicable insulation resistance, dielectric withstanding voltage, and seal requirements, regardless of the acceptability
of the header glass.
The above requirements are not applicable after group B and group C inspections and also not applicable to relays
with spreader pads after forming the leads.
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