ONE-OF-A-KIND CUSTOM ELECTRONIC TEST BENCH ART VINTAGE METERED VARIAC PHOTOS CD For Sale
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ONE-OF-A-KIND CUSTOM ELECTRONIC TEST BENCH ART VINTAGE METERED VARIAC PHOTOS CD:
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ATTENTION:YOU ARE NOT PURCHASING A VARIAC IN THIS LISTING, YOU AREPURCHASING A PHOTO-CD OF AT LEAST 50-IMAGES OF THE VARIOUS CUSTOMVARIACS.
ALL OF THE ITEMS PICTURED IN THIS LISTING ARE ONE-OF-A-KIND,METERED VARIABLE AUTO-TRANSFORMERS (VARIACS), DESIGNED AND HAND-BUILTBY DAVID RIDDLE. THE IDEA WAS TO ELEVATE A MUNDANE FUNCTIONAL DEVICE TOA PIECE OF \"BENCH ART\". OUR CUSTOM VARIACS ARE PRIZED BY TECHNICIANSAND COLLECTORS AROUND THE WORLD FOR THEIR HIGH LEVEL OF CRAFTSMANSHIPAND ERGONOMIC FUNCTIONALITY. THESE \"FANTASY VARIACS\" DIFFER IN THEIRVOLTAGE AND CURRENT RANGES, WHETHER THEY ARE SINGLE OR DUAL METERED,AND WHETHER THOSE METERS ARE ANALOG OR DIGITAL. AESTHETICALLY, SOME AREBASED ON HISTORICAL ELECTRONICS WHILE OTHERS ARE ORIGINAL DESIGNS. EACHITEM IS FULLY TESTED AND COMPLETE WITH A LIMITED LIFETIME WARRANTY (SEEALL OF THE PHOTOS FOR DETAILS, SEE LIFETIME WARRANTY DETAILS BELOW). IFYOU ARE INTERESTED IN HAVING A CUSTOM FANTASY VARIAC MADE, PLEASE CALLUS TOLL-FREE AT TODAY!
IMPORTANTNOTE: THIS IS A BRAND NEW, TOP QUALITY, AMERICANMADEPRODUCT,THAT HAS BEEN COMPLETELY ASSEMBLED IN THE UNITED STATES USING THEFINEST QUALITY AMERICAN MADE COMPONENTS, NOT A POORLY MADE COPY FROMCHINA! WE ONLY SELL THE VERY HIGHEST QUALITY VARIACS FROM U.S.COMPANIES THAT ARE BUILT TO LAST A LIFETIME! (PLEASE CALL FOR FREE LIVE HELP OR TECHNICAL QUESTIONS, AND VISIT OUR store TOSEE OUR VARIACS AND POWER REGULATORS RATED FROM 500-100,000 WATTS!)
IMPORTANTINFORMATION: WE OPERATE A FACILITY THAT EXPERTLY CUSTOMBUILDS THESE VARIAC TYPE AUTOFORMERS FOR ANY VOLTAGE AND CURRENT RATINGFOR U.S. AND INTERNATIONAL STANDARDS.
AFTER CAREFUL ASSEMBLY, EVERY VARIAC IS FULLY TESTED AT THEMAXIMUM RATED LOAD IN OUR FULLY EQUIPPED TEST LAB!
THE FIRST ITEM PICTURED WAS DESIGNED TO LOOK LIKE A VINTAGEGENERAL RADIO PRODUCT BUT BUILT IS A CUSTOM MODEL V20WT3A VARIAC WITHVOLTS AND DUAL RANGE AMPS METERING, CONSTRUCTED WITH ALL AMERICAN MADECOMPONENTS INCLUDING A HOUSING MADE FROM AN ORIGINAL GENERAL RADIOSHIPPING CRATE FROM THE 1940s!
THE SECOND ITEM PICTURED IS A DRCO (DAVID RIDDLE COMPANY)CUSTOM MODEL VA-10VA DUAL ANALOG METERED VARIAC INSPIRED BY 1930sAMPLIFIER RACK EQUIPMENT. BUILT WITH ALL VINTAGE COMPONENTS, THIS ITEMAPPEALS ESPECIALLY TO VINTAGE WESTERN ELECTRIC TUBE AUDIO COLLECTORS.
THE THIRD ITEM PICTURED WAS ORIGINALLY A LEEDS &NORTHRUP RESISTANCE BRIDGE CIRCA 1940 REBUILT INTO A SINGLE METEREDVARIAC FEATURING AN ORIGINAL SOLID MAHOGANY WOOD BOX.
THE FOURTH ITEM PICTURED WAS ORIGINALLY A GENERAL RADIO 874-V1VOLTMETER INDICATOR CONVERTED TO A SINGLE ANALOG METERED VARIAC.
THE FIFTH ITEM PICTURED IS A LEEDS & NORTHRUP VACUUMTUBE VOLTMETER CONVERTED TO A VARIAC.
THE SIXTH ITEM PICTURED WAS ORIGINALLY A LEEDS &NORTHRUP 188822 POTENTIOMETER CONVERTED TO A SINGLE METERED VARIAC THATAPPEARS TO USE THE NICKEL-PLATED CONTACTS AS THE INCREMENTAL VOLTAGEADJUSTMENT.
THE SEVENTH ITEM PICTURED IS A GENERAL RADIO 1800A VACUUM TUBEVOLTMETER CONVERTED TO A VARIAC.
THE EIGHTH ITEM PICTURED IS A DRCO VT10-DVA DUAL DIGITALMETERED VARIAC BUILT INTO THE SHELL OF A TEKTRONIX 109 PULSE GENERATORFROM THE 1960s.
THE NINTH ITEM PICTURED IS A DUAL DIGITAL METERED VARIAC,FEATURING MACHINE CARVED SOLID MICARTA KNOB THAT WAS HAND CONTOURED ANDPOLISHED
THE TENTH ITEM PICTURED IS A VARIAC DESIGNED TO LOOK LIKE ABRAKEMAN\'S STREET CAR SPEED CONTROL
THE ELEVENTH ITEM PICTURED IS A GENERAL RADIO W20M MODIFIED TOA W20MT3A WITH LARGER ANALOG METERS AND KNOB.
THE TWELFTH ITEM PICTURED WAS DESIGNED TO BE USED AS APORTABLE COMPACT BENCH VARIAC. IT FEATURES DUAL ANALOG METERS AND GREENHAMMERTONE FINISH PAINT.
LIFETIMEWARRANTY DETAILS: THIS REBUILT VARIABLE AUTOTRANSFORMER\"VARIAC\", IS PROVIDED WITH A LIMITED LIFETIME WARRANTY ON PARTS ANDLABOR DUE TO DEFECTS IN MATERIALS AND / OR WORKMANSHIP TO THE ORIGINALPURCHASER. PLEASE CALL THE DAVID RIDDLE CO. TO OBTAIN RETURNAUTHORIZATION APPROVAL BEFORE RETURNING ITEM FOR REPAIR (SHIPPINGCHARGES NOT INCLUDED). UPON INSPECTION WE WILL DETERMINE AT OUR SOLEDISCRETION, IF THIS LIMITED WARRANTY APPLIES AND IF SO, THE ITEM WILLBE REPAIRED TO PROPER OPERATING CONDITION. THIS WARRANTY DOES NOT COVERANY OR ALL OF THE FOLLOWING: DAMAGE DUE TO PHYSICAL AND ENVIRONMENTALABUSE, INPUT / OUTPUT OVERLOADING, IMPROPER FUSING, NORMAL COSMETIC /BRUSH WEAR, AND PAINT FINISHES.
Thefollowing is the step-by-step process by which I fully restore bothmetered and non-metered variable autotransformers (\"variacs\") intobetter-than-new condition. Because of my experienceand the qualityof work, I can offer a lifetime warranty on every American-made GeneralRadio, Superior Electric and Staco brand variac that I sell!
1.I perform a full initial evaluation including a \"triage\" test foroperation of all controls and output range for volts and amps, meterfunctions plus a 1,200-volts AC \"HI-POT\" chassis leakage test.
2.I completely disassemble the entire unit and do a full inspection ofall components. All hardware and fasteners (variac assembly,screws,nuts, switch, power cord, wiring, receptacle, handle, knob, meters,dial plate, nameplate, etc.) are separated and stored for individualand unique processing. Two-prong plugs and receptacles arereplacedwith new three-prong types (all wire, metals, etc., not used in thefinal product are recycled).
3. The autotransformer (variac) isfully disassembled into its individual component parts (coil w/terminalplate, rotor, brush assembly, shaft, base-plate, etc.) and the coil and\"brush track\" are cleaned and inspected.
4. If the brush trackhas surface damage, it is \"wet hand-lapped\" with various grades ofabrasives (course to ultra-fine, 150, 220, 400, 600 grit) until it isabsolutely flat and smooth and is then heavily electroplated with asilver alloy for high electrical conductivity and to resistoxidation.After the lapping and silver-plating process is completed, the coilassembly is thoroughly washed with detergent and hot water to removeany remaining silver-plating solution. The coil assembly is then bakedin a custom-made convection oven at 200°F for two hours to completelyremove all moisture and then is allowed to cool.
5. The brass orcopper \"rotating electrical contact\" of the rotor and thebearingsurface of the brass \"brush holder\" are \"wet sanded\" to a smoothfinish, oven dried and after cooling, a special ($100.00+ a tube!)high-temperature, non-spreading synthetic grease is applied to thesliding bearing surfaces (not to the carbon tip!). The brushassemblyis precisely attached to the rotor and checked for full freedom andease of movement.
6. All of the other variac components arecleaned and inspected or replaced with new components. Thevariouscomponents of the variac are then carefully reassembled along with therotating control shaft that has been lubricated with the same syntheticgrease.
7. After the variac is fully assembled, a piece of400-grit sandpaper is placed between the carbon brush tip and thebrush-track with the abrasive face touching the carbon tip.Whileholding the sandpaper, the rotor is rotated back and forth over thesandpaper several times to \"bed\" the carbon tip to the brush track.
8.While the carbon brush tip is being illuminated with a strongbacklight, the rotor is turned through its full sweep observing that nolight is leaking between the carbon tip and the brush track.Thisensures that the carbon brush tip is in intimate physical and henceelectrical contact with the brush track at all times. Anyinterruptionof the intimate contact of the carbon brush tip and the coil brushtrack surface while under electrical load will cause instant andirreparable catastrophic \"arcing\" damage to the brush-track.
9.All of the sheet metal or cast housings and case components (covers,\"shields\", dial-plate, mounting plate, etc.) are washed with degreaser,thoroughly rinsed with hot water and oven dried.
10. Any of thepainted case components that are to be re-painted are stripped usingepoxy stripper, washed with detergent, thoroughly rinsed with hot waterand oven dried.
11. Prior to being repainted, the sheet metalcomponents, are examined for defects (dents, bends, deep scratches,holes, flatness, trueness, etc.) and several custom made tools:\"picks\", \"dollies\", metal, wood and plastic \"forms\", etc., plus varioushammers and files, are utilized for \"pick-and-filing\"-type \"repousse\",hammering out dents and scratches from the inside and filing back theexpanded metal to the original desired form or shape.
12. Anyunwanted holes are filled with a custom-machined metal (aluminum orsteel) \"plug\" that is inserted into the hole that has been \"chamfered\"front and rear. The plug is then secured with a 2-ton pneumatic rivetsqueezer, fitted with polished anvils, that flows the metal plug,filling the hole. Excess metal is carefully filed or sanded flush tothe metal surface providing an invisible and permanent repair whenpainted.
13. All bare-metal surfaces to be painted are fullysanded with various grits of aluminum oxide and/or silicon caroffere(carborundum) sandpapers to provide a \"tooth\" on the metal surface,greatly improving the adhesion of the applied paint finish.Inaddition, all sharp metal edges are \"radiused\" to prevent the paintfrom \"creeping\" away from the edges due to \"surface-tension\"effects.All painted surfaces are \"baked\" or \"cured\" in a 200°F convection ovenfor a minimum of two hours ensuring a well adhered, durable andbeautiful finish.
14. Depending on the condition and thespecific type of the variac\'s circular metal dial plate andmodel/type/specification nameplate (\"litho\" printed, \"silk-screened\" or\"etched\" with paint fill), various methods are utilized in restoringthese components. Before restoring any of these components,theseparts must be washed with detergent, thoroughly rinsed with hot waterand oven dried.
15. Litho-printed plates, if possible, aregenerally touched up by hand using various small brushes andcustom-mixed paints, and are carefully painted while protecting theprinted nomenclature from being painted over. If thenameplate islarge and the damage includes large areas of missing ink or paint, allof the nomenclature (letters, numbers graphic entities, etc.) arecovered with masking tape.
16. I use a brand-new, special,long, thin razor blade and an \"Exacto\" knife, to carefully cut away themasking tape around all of the nomenclature and then the remainingmasking tape is \"stripped\" away. The masked plate is thenspray-painted with the proper background color (usually semi-flatblack). Immediately after painting, I use extreme care, andthe sharptip of the Exacto knife to \"prick\" up the edge of the various pieces ofmasking tape and use a pair of tweezers to carefully peel off the tapewhile not allowing anything to touch the drying paint duringremoval.This process of removing the masking tape while the paint is still wetallows the paint to flow slightly and smooth out the sharp paint lineedge resulting from the masking tape.
17. Etched andpaint-filled type dial and nameplates are first evaluated through \"wetmild abrasion\" using #3/0 stainless-steel wool and water to removeoxidation from the \"raised\" nomenclature and borders and loosening anyfill paint not well adhered.
18. If the fill paint is irregularin surface finish or is missing in spots, the plate needs to be fullystripped with epoxy stripper, washed with detergent, thoroughly rinsedwith hot water and oven dried.
19. The proper color and type offill paint (lacquer works best) is applied in several layers or coatsto build in thickness up to, or just below, the level of the raisednomenclature while allowing each layer to dry for several minutesbetween coats. After the fill painting is complete, the plate is bakedin a 200°F convection oven for a minimum of one hour.
20.Depending on the etched plate\'s substrate material, aluminum, brass ornickel-plated brass, different processes apply. For aluminumand brassplates (or where the nickel plating on the brass has eroded), a metalsanding block (2.5\"L X 1\"W X 1/4\" H) wrapped in 400 grade wet-or-drysandpaper is utilized to \"wet sand\" the plate in a circularmotionunder cold running water.
21. I carefully observe each portion ofthe plate being sanded and note when the raised portions of thenomenclature begin to appear through the fill paint. When theraisednomenclature in the spot being sanded has fully appeared (letters /graphics appear without breaks), I stop sanding in the original spotand move to the next area of the plate until all of the nomenclaturehas been revealed through the fill paint.
22. If small areas ofthe plate are missing fill paint after sanding, it can be carefullyhand touched-up with a small brush to correct any defects. Ifsomeportion of the raised letters or graphics have fill paint still notremoved due to scratches or dents, use a small folded portion of the#400 sandpaper wrapped around the edge of a credit card or thin plasticsheet and carefully and selectively remove the remaining fill paint.
23.For nickel-plated brass plates, I use #1 stainless-steel wool andrunning water to remove the unwanted fill paint. This processtakesmuch longer to reveal all of the nomenclature and requires carefulattention not to cut through the fill paint (no sanding block, onlyyour finger!), but the stainless-steel wool will not scratch the nickelplating; sandpaper will cut through the thin plating almost immediately!
24.The finishing process for all of the plate types is the same-a clearlacquer seal coat. Unfortunately, a glossy finish will clearly revealall of the touch-up work! To eliminate this problem, atextured, clearlacquer finish provides the answer but typically available mattefinishes are not sufficiently textured to hide even minor surfacedefects.
The first step in the texturing process is to placethe plate in a 200°F convection oven for a minimum of ten minutes toreach full temperature evenly across the whole plate. Theheated plateis removed from the oven and immediately placed on a spinning(30-40rpm) painting \"turntable\" while the clear lacquer sprayer (orcan) is held at least 24-inches above the plate allowing the fine mistof droplets to land evenly (because of the rotation) across the entireplate\'s surface.
25. This process is most evenly and easilyaccomplished if a large light source (the sun?) is reflected off of theplate\'s surface at an \"oblique\" or sideways angle. The finelacquerdroplets will be partially drying as they fall to the plate and thenthe heated plate will \"freeze\" them into a uniform and highly texturedfinish. When the finish is not even or is not texturedenough, theplate can be re-heated and re-sprayed for the desired texturaleffect.Test \"coupons\" or sample plates are triedfirst!
26. Whenthe variac is equipped with a single-or multiple-analog meters, thesewill need to be individually cleaned and calibrated.Depending on theage of the particular variac, these analog meters are either housed in\"thermosetting\" bakelite cases with glass \"windows\" or \"thermo-plastic\"cases with painted and clear plastic \"window covers\". Thebakelitecased meters typically use screws to hold the two-part casestogether.Meters with thermo-plastic cases are typically held together with\"snap-on\" front covers that must be carefully pried apart verycarefully so as not to crack the \"styrene\" type plastic that becomeseven more fragile as it ages. In either case, great care mustbeexercised during and after disassembly to prevent damage to theultra-delicate internal meter components (needle, scale, hair-spring,wiring, coils, etc.); one inadvertent hand movement or finger touch tothese components can render the entire meter irreparable!
27.The front cover is washed inside and out using warm water and dish soapand a soft bristled brush to get in the corners and completely rinsedin warm water. The cover is then carefully dried with a\"just-laundered\" and tumble-dried (without softener sheets) plushcotton towel while using a strong \"back light\" to confirm there are nostreaks in the window area and great care is needed not to snag thetiny and fragile \"zero-adjust\" pin that resides in the cover.
28.Unlike meters with glass windows, thermo-plastic covers have windowsthat are very susceptible to surface scratching and must be carefullypolished to eliminate this highly visible and distractingdefect. Veryminor and fine superficial scratches can generally be removed by handwith a commercially available, mildly abrasive, plastic polish and aclean soft cotton cloth. With deeper and more seriousscratches, amulti-step process is usually required. Depending on themeter coverconfiguration, masking of the painted areas of the cover may be neededto prevent damage during this process. The window area isfirst \"wethand-sanded\" with various grades of abrasives (course to ultra-fine,150, 220, 400, 600 grit) until all of the visible scratches have beeneliminated and the window appears upon inspection with a back light tohave a even matte, translucent appearance.
29. While using asoft flannel polishing wheel, rotating at the proper speed and with theappropriate \"polishing-compounds\" for styrene thermo-plastics, Icarefully polish the meter cover window to a crystal-clear, transparentappearance, free of directional polishing marks. This entireprocessmust be monitored visually while using a light touch and continuousmovement to prevent permanent and irreversible damage caused byoverheating and melting of the fragile plastic material.Afterpolishing, the meter cover is again washed to remove any residualpolishing compound and dried.
30. Thermo-plastic meter covershave a strong tendency to acquire and hold a static electricity charge,and this charge can \"lock\" or move the sensitive meter needle up ordown scale rendering the meter inoperative. To continuallydrain offthis static charge, a very thin and transparent coating of clear liquiddish detergent is applied to all of the inside surfaces of the metercover. I use a cotton \"Q-tip\" to spread a tiny amount of detergentevenly inside the cover and then additional clean and dry Q-tips topolish the soap-film to invisibility. This thin film ofdetergent is\"ionic\" and \"hygroscopic\" and absorbs moisture from the air forming aconductive path to discharge any acquired static charge.
31. Thefront and rear meter case components when assembled are designed toform a \"dust-tight\" seal to prevent environmentalcontamination. Ifthese components have been damaged to the point of allowing dirt anddust to enter, the damaged front or rear cover, or both, must bereplaced. If only the front cover is replaced, the rear coverand themeter mechanism must be disassembled and thoroughly cleaned to preventre-contamination after final assembly. During thisdisassembly andcleaning process, the meter mechanism is extremely vulnerable to damageand must be secured in a protected location while cleaning the rearcover. In addition, the meter mechanism itself will often becontaminated and must be meticulously disassembled and cleaned undermagnification as this work requires special tools and the\"hand\" andskill of a watchmaker!
32. Since the meters used in variacs aremeasuring AC voltages and amps or watts, the specific type of metersmost commonly used are of the \"iron-vane\" design and as such aresusceptible to erroneous readings from external magnetic fields, theexact magnetic fields produced by the variac itself! Toprevent theseexternal magnetic fields from affecting the accuracy of the meters,thick-steel \"shield cups\" cover the rear meter covers.
33.After the previous steps have been completed and the meter mechanism,scale and shield cup are all in place, the calibration process canbegin. The first step is \"balancing the tree\" (the movingmetercomponents): the needle, damper vane and the threecounter-weights.The meter is placed in an exact horizontal position with the scalefacing up and the zero-adjust lever is moved until the needle is setprecisely to zero on the scale. When the meter is zeroed, thezero-adjust lever should reside very close to the center of its travel.If it is not, the lever is centered and a fine needle is used to veryslightly bend the hair-spring where it attaches to the zero-lever inthe appropriate direction to achieve a zero reading. If this bendingmethod causes too much deflection of the hairspring from its concentricposition around the pivot, the length of the hairspring must be alteredvery slightly by un-soldering it from the zero-lever and re-solderingat the correct position. \\
34. The meter is raised from thehorizontal to an upright vertical position with the scale facing frontand the scale nomenclature positioned horizontally left toright. Theneedle should remain at the zero position; if it changes to below orabove zero, the direction and amount is noted. While themeter remainsvertical, the meter is rotated 90 degrees clockwise, and the needleposition is noted. The meter is then rotated 180 degreescounter-clockwise, again the needle position is noted.Depending onthe outcome of these tests, each of the three counterweights(bottom-main, left and right) attached to the tree are all adjustedindividually in the appropriate direction along each weights \"arm\" ofthe tree until the meter needle remains at zero position in all of theabove positions to within one half of one \"minor division\" of thescale. Since all of the three counter-weights interact witheach otherduring the tree-balance adjustment process, the meter must becontinually rotated along the various axes while adjusting the threeweights.
35. The electrical calibration of analog iron-vane ACmeters requires a precision calibrated source of volts and ampsaccurate to at least 0.1% over the entire range of the meters to betested. The \"calibrator\" is electrically connected to themeter undertest and the meter is precisely zeroed in the axial position it willusually reside in during use. The calibrator is adjusted tooutput the\"full-scale\" voltage or amps rating of the meter at 50 or 60 hertz(depending where the unit is going to be shipped). Noting thereadingat full-scale, the calibrator is then adjusted to the first\"major-division\" above zero and the reading noted. If both readings arelow or both high in the same amount, a course deflection adjustment ismade. Depending on the type and brand of the specific iron-vane meter,this adjustment is made either by loosening the lock-screw of thedeflection paddle and shifting it\'s position in the \"coil cup\" andre-locking it. On some meters this is accomplished by actually bendingthe paddle\'s position using a small screwdriver. If thescrewdriver ismade of metal, it will have to be moved away from the adjustment areaas its presence will effect the needle position substantially.
36.Adjusting the output of the calibrator to the various major/divisionsacross the meter\'s scale will indicate the \"linearity\" ofcalibration.If the meter is not linear, there is an additional adjustment pointusually to the left of the coarse adjustment point that is utilized tocalibrate the upper portion of the scale. Both of these calibrationpoints interact with each other so it is necessary to continuallychange the output of the calibrator to various major-division setpoints and, in addition, always check the zero set point between teststo confirm it wasn\'t bumped during these adjustments. Throughthe useof both calibration adjustment points the meter should be able to beadjusted to within 2-3% accuracy across the entire scale and veryaccurate at any selected single point such as 120-volts on a 0-150voltmeter for use at American voltage standards.
37. Afterthe meters have been cleaned and calibrated they are re-assembledensuring that there are absolutely no loose dust or dirt particlesremaining in the meter case or visible in or on the windowand thatthe zero pin is lined up with the zero lever so that the external zeroadjustment is working properly. After final re-assembly, the meters arecarefully re-checked visually, mechanically and electrically.
38.The variac knob is usually made of bakelite, and as such, is subject toimpact damage such as chipping and surface scratches, severe chipscannot be repaired so a chipped knob is replaced. Most scratches can bepolished out to a very high sheen. Other knob materialsincludethermo-plastics that are very susceptible to scratching because thematerial is soft, and since it is not heat resistant, polishing isfairly difficult and time consuming. The first step inrestoringeither type of knob is to wash it in hot soapy water using a toothbrushto remove any dirt or finger oil residue. After thoroughlydrying theknob, inspect it to determine the severity of the scratches, deep oneswill not polish out and need to be wet-sanded first using a sequence ofcoarse to fine sandpaper (as described previously in the meter coverrestoration) until a smooth matte finish is obtained.
39. Whileusing a cotton polishing wheel, rotating at the proper speed and withthe appropriate \"polishing-compounds\" for thermo-setting plastics, theknob is polished to a mirror-like \"piano-finish\" appearance, free ofdirectional polishing marks. Since bakelite is a hightemperatureplastic, the polishing process can be fairly aggressive. Whenpolishing a thermo-plastic knob, the entire process must be monitoredvisually while using a light touch and continuous movement to preventpermanent and irreversible damage caused by overheating and melting ofthe fragile plastic material. After polishing the knob it isagainwashed to remove any residual polishing compound and then dried.
40.The final step in the knob restoration is to \"re-fill\" the molded in\"cursor\" or \"pointer\" markings with paint. When any residualpaintremains in the cursor areas, it must be completely removed beforere-filling. The paint used for this application is a\"thinned\" white,gloss enamel, obtained from a can of spray paint dispensed into acup.A long, very thin, camel\'s hair brush, fully filled with paint, istipped into the cursor recess allowing the paint to flow through\"capillary\" action to fully fill the recess. When paint flowsoutsideof the cursor recess, a heat gun is used to partially dry the surfaceof the paint, and a thin plastic card or fingernail is used toscrape-away any excess paint from the knob surface around the cursorrecess.
41. If the variac includes a \"u-shaped\" aluminumcarrying handle, it is first placed on its side on a flat surface todetermine if it is twisted by pushing on each of the tips anddetermining if it is \"rocking\" and not perfectly flat. Thehandle isthen \"trued\" by manually bending or twisting the handle and repeatedlychecking to confirm flatness. The two tips of the handle are\"radius\"sanded on a belt sender to remove any original fabrication \"shearing\"marks as these will be clearly visible when the handle is folded to theback of the variac when it is in use. An abrasive \"scotchwheel\" on arotating arbor is used to evenly \"grain\" the aluminum handle along it\'slength on all surfaces. Soap-filled steel-wool is used in a\"stroking\"linear fashion along the length of the handle to produce abrightlustrous finish. The handle is then washed to remove anyresidue anddried.
42. All \"nickel-plated\" screws, bolts, nuts, washers etc.are \"brightened\" by removing the nickel-oxide from their surfaces bysubmerging them in muriatic \"pool acid\" for ten minutes and thenthoroughly rinsing and \"agitating\" them in continuously running hotwater for a minimum of two minutes. This hardware is driedwith a softcotton towel.
43. Zinc, cadmium and chrome plated parts aremanually restored using hand or powered wire brushes andsteel-wool asthese parts cannot be \"acid washed\". The power cord brassplug-tipsare brightened with sandpaper and soap-filled steel-wool. Thepowercord plug and jacket is first washed with detergent / degreaser and hotwater to remove water- soluble dirt and residue and then thoroughlydried. A lacquer thinner soaked rag is used all along thecord lengthand plug surfaces to remove any hand oils or sticker tape residue.
44.The power cord and all internal wiring that will be soldered duringfinal assembly is \"prepped\" by trimming all wire ends and stripping offan appropriate amount of insulation, twisting the stranded ends andthen individually \"tinning\" each wire end with \"63/37 tin/lead alloy,rosin-core solder\". The tinned wire ends are formed intohooks with\"needle-nose\" pliers for insertion into the various solder tabs andterminal holes of the interconnected internal components.
45.Variac dial plates and name-plates are re-attached to the casecomponents with aluminum rivets, brass eyelets or stainless steel\"drive-screws\". Raised cast-in nomenclature numbers andletters arehand filed or machine/milled to reveal the contrasting aluminum throughthe painted surface to enhance readability. Power cords aresecuredand \"strain relieved\" with either a \"Heyco\" insulated feed-through or arubber grommet and internal cord-clamp.
46. All of therestored components are carefully re-assembled in a specific sequencedetermined in advance by the ease, accuracy and cosmetic protectionrequired for each element or assembly. New, properly-ratedfuseholders are installed and all internal wiring that will be soldered, issecured mechanically prior to soldering. All connections madewith\"solderless, crimp connectors\" are attached to wire ends with a\"ratchet\" type crimper fitted with the proper \"die\" for the individualconnector type and size.
47. During re-assembly, all\"self-tapping\" machine screws and sheet metal screws are discarded andreplaced with either nickel-plated or stainless-steel machinescrews.All threaded holes in castings are \"re-tapped\" with the appropriatemachine tap using a custom-made power tapping tool. All sheetmetalholes that originally accepted sheet-metal screws are drilled to aspecific diameter to accept \"pressed-in, pre-installed nuts\" formachine screw fasteners. Any fasteners that are able to havetheirphillips \"cross-point\" or \"straight-slot\" screwdriver points and \"hexnut-flats\" aligned in a uniform pattern are so aligned for a pleasingcosmetic effect. The polished variac knob is the lastcomponentinstalled to protect it\'s cosmetic appearance. The knob iscarefullyaligned to match dial-plate markings and is securely fastened to thevariac operating shaft.
48. After final assembly has beencompleted, and the overall cosmetic inspection has been completed, theproperly rated fuses are installed, the power switch is placed in the\"on\" position, the knob is positioned mid-scale and the power cord isplugged into a \"hi-pot\", high-voltage (1,200vac) test source.The highvoltage is applied between both \"hot\" and \"neutral\" power cord pins andthe variac chassis for a one-minute insulation test.
49. Afterthe variac has successfully passed the high-voltage insulation test,the power cord is plugged into a specially-configured metered variacthat is brought up slowly to the full rated input voltage of variacunder test, and the \"quiescent\" or no-load excitation current ismeasured as the variac knob is rotated through it\'s entirerange. Thevariac knob is rotated fully counter-clockwise and the test variac\'soutput is connected to a precision \"instrumented\" load that isconfigured to provide a zero to full load to the test variac.If thevariac under test is metered, the meters will again be checked atseveral test voltages and currents to confirm that they meet thecalibration specifications.
50. The last restoration step isaffixing a DRCO label printed with a toll-free telephone number to therear or bottom of the variac confirming that the previously describedrestoration process has been completed and the variac is now guaranteedfor life!
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