MIL-PRF-21038F
TABLE III. Sampling plans for group A and group B inspections.
Lot size
Group A, group II inspections
Group B
1 to
5
100 percent
100 percent
6 to
13
100 percent
5
14 to
50
13
5
51 to
90
13
7
91 to
150
13
11
151
to
280
20
13
281
to
500
29
16
501
to
1,200
34
19
1,201
to
3,200
42
23
3,201
to
10,000
50
29
4.6.3 Group B inspection (M level and T level only). Group B inspections shall consist of the inspections
specified in table IV in the order shown. A sample of parts shall be selected from each inspection lot in
accordance with table III. If one or more defects are found, the lot shall be screened for that defect, and defects
removed. A new sample of parts shall be randomly selected again in accordance with table III. If one or more
defects are found in the second sample for the same defect or rejection cause, the lot shall be rejected and shall
not be supplied to this specification. Sample units which have passed group B inspections (except for
solderability samples) may be delivered on the contract provided the samples still meet specification
requirements.
TABLE IV. Group B inspection (M level and T level only).
Inspection
Requirement paragraph
Method paragraph
Dielectric withstanding voltage
3.7
4.7.4
Insulation resistance
3.8
4.7.5
4.7 Methods of examination and test.
4.7.1 Visual and mechanical examination (see 3.4, 3.21, and 3.22). Transformers shall be examined to verify
that the materials, external interface and physical dimensions, marking, and workmanship are in accordance
with the requirements of this specifications.
4.7.2 100 percent screening (T level only) (see 3.5). T level transformers shall be subjected to thermal shock
screening in accordance with MIL-STD-202, method 107, test condition A (5 cycles). The temperature for step
3 shall be the maximum operating temperature for the class of transformer (see 3.1). Following the thermal
shock screening, the winding continuity test shall be performed on all transformers.
4.7.3 Electrical characteristics (including waveform parameters (see 3.1 and 3.6). Waveform parameters
shall be measured as specified in 3.1. Electrical characteristics shall also be measured as specified in 4.7.3.1
through 4.7.3.4.
4.7.3.1 DC resistance (primary and secondary). The primary and secondary resistance of the windings shall
be measured at or corrected to 25°C ±5°C.
4.7.3.2 Primary inductance. The primary inductance of the windings shall be measured at the specified pulse
amplitude and pulse repetition rate (see 3.1).
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