TO 1-1-700 - Robins Air Force Base

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TO 1-1-700 • Tube clamps. • Miniature tube shields. • Plug-in relays. • Pressure-contact grounds. • Coaxial test points or receptacles. • Windows, lenses, etc. • Transparent plastic parts. • Plastic materials such as polyethylene, polystyrene, polyamide, acrylic, silicone, epoxy (other than printed wiring boards) melamine-fiber-glass, fluorocarbon, vinyl, and alkyd. • Materials used for their specific arc-resistant properties and classified as such. 8.8.3.3.1.2 Electrical contacts, contact portions, or mating surfaces of binding posts. Also connectors, fuses, jacks, keys, plug, and relay sockets (including tube sockets, switches and test points). 8.8.3.3.1.3 Mechanical parts. 8.8.3.3.1.4 Surfaces which rub together for electrical or magnetic contact. For example, bearings, contact fingers, potentiometers, shafts, shields, and variable auto-transformers. 8.8.3.3.1.5 Surfaces whose operational temperature exceed 266 ºF (130 ºC) or whose operating temperatures will cause carbonization or smoking. 8.8.3.3.2 Application. The varnish coating shall be applied by spraying, brushing, dipping, or any combination. The dried film shall have a clear, smooth finish (free from bubbles, wrinkles, filaments, or spray dust). The running, lumping, or gathering of the film into drops shall be avoided. Where practical, the dry film thickness shall be at least 2.0 mils (0.002 inch). 8.8.3.3.2.1 Spraying. For larger equipment, a pressure pot spray gun with a tip regulated to give a wet spray is recommended. For small compact equipment, a pencil spray tip, regulated to give a narrow wet spray, is recommended. The varnish shall be applied in a wet coat over all parts to prevent the formation of fuzz or filaments. A dry spray which forms spray dust shall not be used. The equipment or individual assembly shall be sprayed from as many angles as necessary to assure complete coverage with a wet coat. If more than one coat of varnish is applied, sufficient drying time should be allowed between each coat. 8.8.3.3.2.2 Brushing. All parts which cannot be reached by spray shall be coated as completely as practicable with a brush. A brush may also be used to cover small areas not covered during the spraying process. On those components requiring extensive masking, brush application of the coating material may prove more efficient than spray application. 8.8.3.3.2.3 Dipping. Subassemblies or components may be coated by dipping, provided all requirements are met. 8.8.3.3.3 Curing of Varnish. Equipment coated with varnish shall be dried by heating to 130 °F (54 °C). Heating shall be gradual to prevent shrinking, cracking, warping, or other deterioration of the parts or materials. The drying temperature should be maintained for at least 1/2 hour but not longer than 3 hours. Drying may be done in a vented oven, vacuum oven, or with an A-A-59435 Hot Air Gun (shop use only). 8.8.3.3.4 Precautions. The following equipment requires special precautions for the application of varnish: 8.8.3.3.4.1 Radio Receivers and Transmitters. The application of varnish will cause changes in some of the circuit constants. These changes may be discernible only by electrical tests and measurements. A change in alignment may be noted immediately after application of the varnish. As the varnish dries and ages, further changes in circuit constants may take place. The greatest change ordinarily will occur within 72 hours after treatment. The set should be completely realigned at the end of that period. 8.8.3.3.4.2 Coil Shields. When coil shields are removed and replaced, they can be damaged and alter the tuning adjustments. If the damage is great, proper alignment is impossible. Extreme care must be exercised in removing and replacing coil shields. 8.8.3.3.4.3 Trimmer Capacitors. Avoid spraying or brushing varnish on the plates of trimmer capacitors. To minimize damage, all trimmer capacitors should be completely covered during coating. If these capacitors fail to operate satisfactorily after treatment, make a thorough inspection for deposits of varnish. 8.8.3.3.4.4 Tuning Slugs. Extreme care must be taken in removing and replacing tuning slugs. If varnish is accidentally applied to a slug, remove it before replacing the slug. 8.8.3.3.4.5 Discriminator Circuits. Careful adjustment of discriminator circuits after treatment is essential, especially in the case of frequency-modulated receivers. Discriminator circuits are more susceptible to change in circuit constants caused by varnish than other part. 8-36
TO 1-1-700 8.8.3.3.4.6 Tuned Circuits. Be especially careful during masking to ensure that wires associated with tuned circuits are not moved. Movement of such wires may cause changes in circuit values. 8.8.3.3.4.7 Relays. Deposits of varnish on the armature, pivots, or similar components will cause the relays to bind. The whole relay should be carefully masked until after spraying has been completed. A brush should be used to coat the coils and leads after the masking has been removed. Relays with palladium-tipped contacts should be removed before application of varnish. 8.8.3.3.4.8 Meters. Since meters are easily damaged by a the varnish spray treatment, all meters must be checked for accuracy before treatment. Some meters may be affected by heat. In other instances, meter magnets may be affected by magnetic fields that exist around drying equipment. Refer to the applicable service directives for instructions on varnish spray treatment of meters. If guidance is not available, do not apply varnish. 8.8.4 Sealants. Sealants are another type of protective film used in C-E-M equipment. Sealants are either liquids or pastes which solidify after application. They form a flexible seal, preventing moisture intrusion at mechanical joints, spot-welds, and threaded closures. In addition, sealants prevent entry of corrosive environments to faying surfaces, fastener areas, exposed landing gears switches, and other metal-encased avionic equipment. They function principally as waterproof barriers. It is therefore very important that damaged sealants be repaired as soon as possible. Detailed information on sealants can be found in Chapter 12 of this manual. 8.8.4.1 Suitable for Electronics. The following sealants are approved for use on electronic equipment: 8.8.4.1.2 MIL-A-46146 Adhesive-Sealant, Silicone, RTV, Non-Corrosive is used for sealing avionic equipment in areas where temperatures are between 250 ºF (121 ºC) to 350 ºF (177 ºC). MIL-A-46146 RTV Coating, Flowable, Brush Application is used for encapsulating and sealing of electrical and electronic components. This material has good resistance for oxidation, weathering, and water. MIL-PRF-81733, SEALING AND COATING COMPOUND, CORROSION INHIBITIVE 48 8.8.4.1.3 MIL-PRF-81733 Sealing and Coating Compound can be used to seal gaps, seams, and faying surfaces with temperatures up to 250 °F (121 °C). This material is applied by brush. 8.8.4.2 Unsuitable for Electronics (Containing Acetic Acids). Any RTV silicone sealant that gives off acetic acid during its cure cycle is corrosive and shall not be used on electronic components. 8.9 HANDLING OF SPECIFIC EQUIPMENT/COMPO- NENTS. When corrosion is detected, the methods used for removal and repair shall be based primarily on the material substrate. However, some components have special requirements based on their function or operational environment. 8.9.1 Bonding/Grounding. Electrical bonding provides a low resistance electrical path between two or more conductive units or components. Grounding is a form of bonding that utilizes the primary structure as a portion (return path) of the electrical circuit. 8.9.1.1 Cleaning and Corrosion Removal. AMS-S-83318, SEALING COMPOUND, LOW TEMPERA- TURE CURING 10 8.8.4.1.1 AMS-S-83318 Sealing Compound, Low Temperature Curing, is a quick cure sealant used for sealing gaps and depressions on areas during extreme cold activities. Apply with an A-A-3077, Style T Typewriter Brush. a. Remove all dirt, oil, and grease from a circular area slightly larger than the connection. This area should correspond to about 1-1/2 times the diameter of the connection. Use an A-A-59323, Type II Cleaning Cloth, dampened with Cleaning Solvent. b. If more vigorous soil removal is required, scrub with an A-A-3077 Typewriter Brush until all contaminants are removed. c. Wipe with a dry A-A-59323 Type II Cleaning Cloth. MIL-A-46146, ADHESIVE/SEALANT, SILICONE RTV, NON-CORROSIVE, GROUP I/II/III, TYPE I OR GROUP I, TYPE II 19 d. Remove paint, anodize, or conversion coating film and surface corrosion from the planned attachment area with a A-A-58054, Type I, Grade B Abrasive Mat. For corrosion beyond the surface corrosion stage, refer to TO 1-1-691. 8-37
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TO 1-1-700 TECHNICAL MANUAL CORROSI
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TO 1-1-700 TABLE OF CONTENTS Chapte
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TO 1-1-700 TABLE OF CONTENTS - CONT
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TO 1-1-700 LIST OF ILLUSTRATIONS -
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TO 1-1-700 FOREWORD 1. PURPOSE. The
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TO 1-1-700 List of Related Publicat
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TO 1-1-700 SAFETY SUMMARY 1. GENERA
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TO 1-1-700 AMS-G-6032, GREASE, PLUG
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TO 1-1-700 MIL-DTL-64159, COATING,
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TO 1-1-700 MIL-PRF-27617, GREASE, A
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TO 1-1-700 O-L-164, DRESSING, LEATH
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TO 1-1-700 MIL-T-81772, THINNER, PO
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TO 1-1-700 tronics equipment and th
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TO 1-1-700 cleaning situation, syst
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TO 1-1-700 c. Riveted joints shall
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TO 1-1-700 c. Remove and replace an
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TO 1-1-700 MIL-L-87177, LUBRICANT,
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TO 1-1-700 Figure 3-1. Simplified C
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TO 1-1-700 resistant, and also at t
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TO 1-1-700 is first noticeable as a
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TO 1-1-700 3.7.8 Oxygen Concentrati
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TO 1-1-700 Figure 3-14. Concentrati
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TO 1-1-700 Figure 3-17. Galvanic Se
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TO 1-1-700 Figure 3-20. Aluminum Su
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TO 1-1-700 3.8.7 CRES/Stainless Ste
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TO 1-1-700 3.9.10 Climate. Warm, mo
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TO 1-1-700 3.11 PREVENTATIVE MAINTE
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TO 1-1-700 CHAPTER 4 COMPOSITE AND
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TO 1-1-700 4.4.4.4 Glass parts shal
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TO 1-1-700 CHAPTER 5 PACKAGING (STO
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TO 1-1-700 extent of damage dependi
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TO 1-1-700 5.15 PRECAUTIONS FOR VCI
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TO 1-1-700 c. Secure the desiccant
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TO 1-1-700 Figure 5-8. Shock Isolat
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TO 1-1-700 Figure 5-9. Examples of
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TO 1-1-700 5.24.10 Rigid or Flexibl
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TO 1-1-700 CHAPTER 6 MOISTURE AND F
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TO 1-1-700 c. 6.2.6 Felt. Examine f
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TO 1-1-700 a. After first directing
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TO 1-1-700 6.4.5.14 Terminals, scre
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TO 1-1-700 NOTE • Authorized clea
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TO 1-1-700 Table 7-1. Cleaning of S
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TO 1-1-700 7.3.1.2.3 Portable, 45 g
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TO 1-1-700 Table 7-2. Common Milita
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TO 1-1-700 inactivity, storage, or
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TO 1-1-700 7.5.6.5.1 Grade 1 - A th
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TO 1-1-700 Table 7-4. Corrosion Pre
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TO 1-1-700 Table 7-5. Preservation
Page 114 and 115: TO 1-1-700 either case, MIL-PRF-269
Page 116 and 117: TO 1-1-700 MIL-PRF-85285, COATING,
Page 118 and 119: TO 1-1-700 c. Cadmium plated surfac
Page 120 and 121: TO 1-1-700 a. Scuff sand and feathe
Page 122 and 123: TO 1-1-700 7.7.7.2 If surface is no
Page 124 and 125: TO 1-1-700 7.7.9.2 Where only parti
Page 126 and 127: TO 1-1-700 7.8.1 Type I Application
Page 128 and 129: TO 1-1-700 Extend (Loctite) 32150 J
Page 130 and 131: TO 1-1-700 There are three ways to
Page 132 and 133: TO 1-1-700 vulnerable surfaces clea
Page 134 and 135: TO 1-1-700 Table 8-2. Materials, Th
Page 136 and 137: TO 1-1-700 Table 8-4. Electronic Cl
Page 150 and 151: TO 1-1-700 Table 8-5. Accessories o
Page 152 and 153: TO 1-1-700 Table 8-5. Accessories o
Page 154 and 155: TO 1-1-700 f. Devices with permanen
Page 156 and 157: TO 1-1-700 Table 8-7. Cleaning and
Page 158 and 159: TO 1-1-700 MIL-PRF-87937, CLEANING
Page 160 and 161: TO 1-1-700 of contamination). Maint
Page 162 and 163: TO 1-1-700 8.8.2 Protective Coating
Page 166 and 167: TO 1-1-700 a. For bonding/grounding
Page 168 and 169: TO 1-1-700 vertently destroy the mo
Page 170 and 171: TO 1-1-700 doors, and other corrosi
Page 173 and 174: TO 1-1-700 CHAPTER 10 CORROSION PRO
Page 175 and 176: TO 1-1-700 MIL-PRF-81733, SEALING A
Page 177 and 178: TO 1-1-700 d. After corrosion is re
Page 179 and 180: TO 1-1-700 (3) Stainless/CRES steel
Page 181 and 182: TO 1-1-700 10.9 WATER ENTRAPMENT AR
Page 183 and 184: TO 1-1-700 f. Shield equipment from
Page 185 and 186: TO 1-1-700 b. Use e-inch rivnuts of
Page 187 and 188: TO 1-1-700 10.17.3 If the plating s
Page 189: TO 1-1-700 Figure 10-16. Dissipatio
Page 192 and 193: TO 1-1-700 (2) If allowable damage
Page 194 and 195: TO 1-1-700 Table 11-1. Recommended
Page 196 and 197: TO 1-1-700 11.6 3M CO. SCOTCH-BRITE
Page 198 and 199: TO 1-1-700 11.11.2 Control of Mecha
Page 200 and 201: TO 1-1-700 11.12.2 Mechanical Damag
Page 202 and 203: TO 1-1-700 MIL-DTL-81706 (ALODINE),
Page 204 and 205: TO 1-1-700 11.13.2.3 Application of
Page 206 and 207: TO 1-1-700 only when there is no da
Page 208 and 209: TO 1-1-700 NOTE SEMCO PASA-JELL 101
Page 210 and 211: TO 1-1-700 (CRES), lead, ceramic, g
Page 212 and 213: TO 1-1-700 11.13.7.2 Treatment of C
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TO 1-1-700 MIL-A-46106, ADHESIVE/SE
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TO 1-1-700 Table 12-1. Sealing Comp
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TO 1-1-700 used to apply sealants i
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TO 1-1-700 Figure 12-2. Sealant App
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TO 1-1-700 Figure 12-4. Rivet Appli
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TO 1-1-700 Figure 12-6. Sealant Inj
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TO 1-1-700 below and adhere very po
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TO 1-1-700 Table 12-2. Time Require
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TO 1-1-700 Table 12-2. Time Require
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TO 1-1-700 of 20 to 25 seconds in a
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TO 1-1-700 d. Remove all uncured se
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TO 1-1-700 MIL-PRF-81733, SEALING A
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TO 1-1-700 MIL-PRF-81733, SEALING A
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TO 1-1-700 Figure 12-12. Typical Me
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TO 1-1-700 may be used for low temp
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TO 1-1-700 Figure 12-14. Sealing Pr
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TO 1-1-700 - Robins Air Force Base

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