1、AMSC N/A FSC 5960 INCH-POUND MIL-DTL-24251F 11 July 2013 SUPERSEDING MIL-DTL-24251E 15 February 2008 DETAIL SPECIFICATION SHIELDS, RETAINERS (BASES), AND ADAPTERS, ELECTRON TUBE, HEAT DISSIPATING GENERAL SPECIFICATION FOR This specification is approved for use by all Departments and Agencies of the
2、Department of Defense. 1. SCOPE 1.1 Scope. This specification covers the general requirements for heat dissipating electron tube shields, associated retainer (bases), and adapters for use in electronic equipment (see 6.1). 1.2 Part or Identifying Number (PIN). The PIN (when applicable) consists of t
3、he letter M, the basic number of the specification sheet, and an assigned dash number (see 3.1), as shown in the following example: M24251 /XX -XXXX Designator Specification Dash number sheet number (See specification sheet) 2. APPLICABLE DOCUMENTS 2.1 General. The documents listed in this section a
4、re specified in sections 3 and 4 of this specification. This section does not include documents cited in other sections of this specification or recommended for additional information or as examples. While every effort has been made to ensure the completeness of this list, document users are caution
5、ed that they must meet all specified requirements documents cited in sections 3 and 4 of this specification, whether or not they are listed. 2.2.1 Specifications, standards, and handbooks. The following specifications, standards, and handbooks form a part of this document to the extent specified her
6、ein. Unless otherwise specified, the issues of these documents are those cited in the solicitation or contract (see 6.2). DEPARTMENT OF DEFENSE SPECIFICATIONS MIL-DTL-12883 - Sockets and Accessories for Plug-in Electronic Components, General Specification for. MIL-DTL-24251/3 - Shield, Electron Tube
7、, Heat Dissipating, 7 and 9 Pin, Miniature (Split Shell) (Inactive for New Design) MIL-DTL-24251/4 - Retainer (Base), and Adapter, Electron Tube, Heat Dissipating, 7 and 9 Pin, Miniature MIL-DTL-24251/5 - Shield, Electron Tube, Heat Dissipating, 7 and 9 Pin, Miniature (Open Sides) MIL-DTL-24251/6 -
8、Shield, Electron Tube, Heat Dissipating 7 and 9 Pin, Miniature (Retrofit Type Only) Comments, suggestions, or questions on this document should be addressed to DLA Land and Maritime, ATTN: VAT, P.O. Box 3990, Columbus, OH 43218-3990, or to TubesAmpsdla.mil. Since contact information can change, you
9、may want to verify the currency of this address information using the ASSIST Online database at https:/assist.dla.mil/. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-DTL-24251F 2 DEPARTMENT OF DEFENSE STANDARDS MIL-STD-130 - Identification Mark
10、ing of U.S. Military Property. MIL-STD-202 - Electronic and Electrical Component Parts. MIL-STD-889 - Dissimilar Metals MIL-STD-1285 - Marking of Electrical and Electronic Parts. (Copies of these documents are available online at http:/quicksearch.dla.mil/ or https:/assist.dla.mil/ or from the Stand
11、ardization Document Order Desk), 700 Robbins Avenue, Building 4D, Philadelphia, PA 19111-5094.) 2.3 Non-Government publications. The following documents form a part of this document to the extent specified herein. Unless otherwise specified, the issues of these documents are those cited in the solic
12、itation or contract. AMERICAN SOCIETY FOR TESTING AND MATERIALS (ASTM) ASTM-A342/A342M - Materials, Feebly Magnetic, Permeability of. Standard Test Methods For (Applications for copies can be found online at http:/www.astm.org/ or should be addressed to the American Society for Testing and Materials
13、 (ASTM), 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959.) ELECTRONIC COMPONENTS ASSOCIATION (ECA) ECA-RS209 - Electron Tubes. (Copies of these documents are available online at http:/ or Global Engineering Documents, Attn: Customer Service Department, 15 Inverness Way East, Englewood, CO 80
14、112-5776.) NATIONAL CONFERENCE OF STANDARDS LABS (NCSL) NCSL-Z540.3 - Requirements for Calibration of Measuring and Test Equipment. (Applications for copies can be found online at http:/www.ncsli.org or should be addressed to the National Conference of Standards Labs (NCSL), 1800 30th Street, Suite
15、305B, Bolder, CO. 80301.) 2.4 Order of precedence. In the event of a conflict between the text of this document and the references cited herein (except for related specification sheets), the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and reg
16、ulations unless a specific exemption has been obtained. 3. REQUIREMENTS 3.1 Specification sheets. The individual part requirements shall be as specified herein and in accordance with the applicable specification sheet. In the event of any conflict between requirements of this specification and the i
17、ndividual specification sheet, the latter shall govern. 3.2 Material. The material shall be as specified (see 3.1). When a definite material is not specified, a material shall be used which will enable the tube shields, retainers (bases), and adapters to meet the requirements of this specification.
18、Acceptance or approval of any constituent material shall not be construed as a guaranty of the acceptance of the finished product. 3.2.1 Dissimilar metals. Where dissimilar metals are used in intimate contact with each other, protection against corrosion shall be provided. Dissimilar metals must be
19、as recommended in MIL-STD-889. 3.3 Design, construction, and physical dimensions. The tube shields, retainers (bases), and adapters shall be of the design, construction, and physical dimensions specified (see 3.1). The design shields, retainers (bases), and adapters shall be such that they will moun
20、t to the chassis using the same hardware (including screws), as that of the applicable tube socket. 3.3.1 Finish. Unless otherwise specified (see 3.1), tube shields, retainers (bases), and adapters shall be treated with a black matte finish. That portion of the mating shield and retainer (base) or r
21、etainer (base) and chassis where low electrical resistance is required may be finished with other than black matte. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-DTL-24251F 3 3.3.2 Pure tin: The use of pure tin, as an underplate or final finish
22、, is prohibited both internally and externally. Tin content of electron tube components and solder shall not exceed 97 percent, by mass. Tin shall be alloyed with a minimum of 3 percent lead, by mass (see 6.3). 3.3.3 Liners. Shields shall be constructed in such a way that the liners are securely ret
23、ained in position within the shield (see 3.5.3). Liners with circumferential corrugations or other configurations that could allow tube breakage and that do not permit spring action within the shield to allow for maximum tube diameter variations are not acceptable. 3.3.4 Installation and removal. De
24、sign of the shield shall be such that installation and removal of the shield from a seated electron tube shall not scratch or damage the electron tube envelope when tested as specified in 4.5.3.4. Unless otherwise specified, no tool shall be required for installation or removal of the shield from th
25、e tube or retainer (base) or adapter. 3.3.5 Spring retention. When used (see 3.1), the coil spring shall be securely retained within the shield. The free end of the spring, or the loop that makes contact with the electron tube envelope shall be at least seven-eighths of a complete turn and the sprin
26、g tip shall not touch the tube envelope. 3.3.6 Retainer (base) and adapter. The retainer (base) and adapter design shall be such that it rigidly retains the tube shield during all tests and examination of this specification. 3.4 Permeability. All parts shall be made from materials that are classed a
27、s nonmagnetic. The permeability of the tube shield assembly shall be less than 2 (air = 1.0) (see 4.5.2). 3.5 Installation, locking and unlocking torque or load, and removal force. 3.5.1 Initial force. The installation, locking and unlocking torque or load, and removal forces necessary to install an
28、d remove the shield over the applicable slug (see figure 1) and retainer (base), and adapter shall be not greater than specified on the applicable specification sheet (see 3.1), when tested in accordance with 4.5.3.1. 3.5.2 Force at temperature extremes. The installation, locking and unlocking torqu
29、e or load, and removal force shall be not greater than 150 percent nor less than 50 percent of the initial force when tested at 85C 5C and -55C 5C, in accordance with 4.5.3.2. 3.5.3 Fatigue. When tested in accordance with 4.5.3.3, the installation or removal force shall be not greater than 125 perce
30、nt nor less than 50 percent of the initial force and the liner shall remain in position within the shield. 3.6 Vibration. When tested in accordance with 4.5.4, the shield shall not loosen from the retainer (base) or adapter. There shall be no evidence of damage to the shield, or retainer (base), and
31、 adapter, nor the glass envelope of the electron tube, during installation, during the test, or upon removal after the test. 3.7 Shock. When tested in accordance with 4.5.5, the shield shall not loosen from the retainer (base) or adapter as applicable, and there shall be no evidence of damage to the
32、 shield, tube socket, shield retainer (base), or the glass envelope of the electron tube. 3.8 Heat resistance. When shields, retainers (bases) and adapters are tested in accordance with 4.5.6, there shall be no peeling, blistering, chipping, or pitting of the finish. 3.9 Heat dissipation. The averag
33、e reduction of a minimum of two surface temperature readings of the instrumented tube shall be not less than the value specified (see 3.1), when tested in accordance with 4.5.7.1. 3.10 Salt atmosphere (corrosion). When shields, retainers (bases) and adapters are tested as specified in 4.5.8, there s
34、hall be no evidence of corrosion and the finish shall not peel, blister, chip, or pit. 3.11 Electrical contact. The dc resistance from the shield to the chassis shall be not greater than 1 ohm when tested in accordance with 4.5.9. 3.12 Marking. Each tube shield, retainer (base), or adapter shall be
35、permanently and legibly marked in accordance with MIL-STD-130 with the following: a. Military Part or Identifying Number (PIN). b. Date and source code in accordance with MIL-STD-1285. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-DTL-24251F 4
36、3.13 Recycled, recovered, or environmentally preferable materials. Recycled, recovered, or environmentally preferable materials should be used to the maximum extent possible, provided that the material meets or exceeds the operational and maintenance requirements, and promotes economically advantage
37、ous life cycle costs. 3.14 Workmanship. Shields and associated parts shall be processed in such a manner as to be uniform in quality and shall be free from pits, corrosion, cracks, rough edges, chips, spalls and other defects that will affect life, serviceability, or appearance. 4. VERIFICATION 4.1
38、Classification of inspections. The inspection and testing of electron tube shields, retainers(bases) and adapters shall be classified as conformance inspection. a. Inspection conditions (see 4.3). b. Conformance inspection (see 4.4). 4.2 Test equipment and inspection facilities. The contractor shall
39、 establish and maintain a calibration system in accordance with NCSL-Z540.3. 4.3 Inspection conditions. Unless otherwise specified herein, all inspections shall be made in accordance with the general requirements of MIL-STD-202. 4.4 Conformance inspection. 4.4.1 Inspection of product for delivery. I
40、nspection of product for delivery shall consist of groups A and B inspection. 4.4.1.1 Inspection lot. An inspection lot shall consist of tube shields, retainers (bases), or adapters of the same design and size, produced under essentially the same conditions and offered for inspection at one time. 4.
41、4.1.2 Rejected lots. If an inspection lot is rejected, the contractor may rework it to correct the defects, or screen out the defective units, and resubmit for reinspection. Such lots shall be separate from new lots, and shall be clearly identified as reinspected lots. 4.4.1.3 Group A inspection. Gr
42、oup A inspection shall consist of the inspections specified in table I, in the order shown. TABLE I. Group A inspection. Examination Requirements paragraph Method paragraph Visual and mechanical examination 3.2 through 3.3.5 and 3.13 4.5.1 Provided by IHSNot for ResaleNo reproduction or networking p
43、ermitted without license from IHS-,-,-MIL-DTL-24251F 5 4.4.1.3.1 Sampling plan. Statistical sampling and inspection shall be performed on an inspection lot basis with a random sample of components selected in accordance with table II. The acceptance levels shall be based upon the zero defective samp
44、ling plan. No failures shall be permitted. TABLE II. Group A sampling plan. Lot size Sample size 1 - 13 14 - 150 151 - 280 281 - 500 501 - 1,200 1,201 - 3,200 3,201 - 10,000 10,001 - 35,000 35,001 - 150,000 150,001 - 500,000 500,001 and over 100 percent 13 20 29 34 42 50 60 74 90 102 4.4.1.4 Group B
45、 inspection. Group B inspection shall consist of the inspections specified in table III, in the order shown, and the sample shall be selected from inspection lots that have passed group A inspection. NOTE: If the following group B tests have previously been performed by the tube shield manufacturer,
46、 and if the material, manufacturing process, and test requirements are the same as when these tests were initially performed, the subject test(s) need not be performed again. TABLE III. Group B inspection. Test Requirement paragraph Method paragraph Heat resistance - - - - - - - - - - - - - - - - -
47、- - - - - - - - - Heat dissipation - - - - - - - - - - - - - - - - - - - - - - - - - Permeability - - - - - - - - - - - - - - - - - - - - - - - - - - - - Installation and removal - - - - - - - - - - - - - - - - - - - - Salt atmosphere (corrosion) - - - - - - - - - - - - - - - - - Electrical contact
48、- - - - - - - - - - - - - - - - - - - - - - - - - Installation, locking and unlocking torque or load, and removal force - - - - - - - - - - - - - - - - - - - - - - - Initial force at 25C - - - - - - - - - - - - - - - - - - - - - Force at temperature extremes - - - - - - - - - - - - - Fatigue - - - -
49、 - - - - - - - - - - - - - - - - - - - - - - - - - - Vibration - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Shock - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 3.8 3.9 3.4 3.3.4 3.10 3.11 3.5 3.5.1 3.5.2 3.5.3 3.6 3.7 4.5.6 4.5.7 4.5.2 4.5.3.4 4.5.8 4.5.9 4.5.3 4.5.3.1 4.5.3.2 4.5.3.3 4.5.4 4.5.5 4.4.1.4.1 Sampling plan. Sample units shall be selected from tube shields,
