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Conventional Fixtures Altman 8" Fresnel Arcing

Discussion in 'Lighting and Electrics' started by lieperjp, Feb 3, 2009.

  1. lieperjp

    lieperjp Well-Known Member

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    So recently we've been having problems with some of our fresnels (Altman 8" Fresnels.) The lamps get about 50-100 hours (?) on them and then they stop working. The filaments are fine, and all we have to do is use some fine sand paper on the contacts of the lamp and they start working again. It happened to one of my lamps tonight and it looks like arcing. Where's a good place to buy new bases for Altman Fresnels?
     
  2. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    re: Altman 8" Fresnel Arcing

    It should be a simple order a new socket from any Altman dealer (which means almost everyone). Call your local dealer. If you don't have one or you don't like them then the big national dealers like Barbizon, 4Wall, or BMI can help you. You could hit the internet Production Advantage can probably get them for you. You can give our own [user]BillESC[/user] a yell and see if he can get them for you. You may even be able to order the parts directly from Altman at 1-800-4-Altman.
     
  3. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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  4. lieperjp

    lieperjp Well-Known Member

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  5. photoatdv

    photoatdv Active Member

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    re: Altman 8" Fresnel Arcing

    Just a thought.... Since that is a large base, couldn't you sand the corrosion out of the base( carefully, you don't want to take off any more than absolutely necessary) and the lamp at the same time, then it might not do it again. The lamps keep corroding because the socket is corroded and if one is, it will corrode the other. Just make sure it is safely unplugged if you try this!
     
  6. gafftaper

    gafftaper Senior Team Senior Team Fight Leukemia

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    re: Altman 8" Fresnel Arcing

    Working off of Photoatdv's idea. Could you carefully sand out the base and then give it some sort of chemical treatment to reduce the return of corrosion? I'm not a chemist and this may be a bad or pointless idea.

    If the street price is anywhere close to the list price you might want to think about new Fresnels.

    Is there another lamp that can be used with a cheaper base? Ship?
     
  7. lieperjp

    lieperjp Well-Known Member

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    Well, I have good news/bad news. Apparently we have some new sockets - I think we have two of them. The only problem is that we have them because some the fresnels were doing this from brand new. Apparently Altman sent us new sockets for free. Just another proof that arcing spreads like a virus. :doh: (These are about 10 years old - I think. No more than 15 years old.)
     
  8. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    Closest would probably be the 1000W BTR in a medium prefocus socket, but would require serious modification to mount the socket at the proper height, due to the lamps' different LCLs. Then the socket and base would be blocking the lower portion of the reflector, so a smaller reflector would be needed. The smaller reflector means less output, and Fresnels are not very efficient to start. :(

    Just buy the ~$50 street price socket, unless you're in a position to consider purchasing new fixtures.

    Interesting aside is that at least one manufacturer has made a "stage" version of 8" FS with a MogPF socket and a "studio" version with a MogBP socket. At higher wattages the mogul bipost is much preferred.
     
  9. Clifford

    Clifford Active Member

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    We had a similar problem with a few of our 75Qs, with corrosion and whatnot. The symptom we had was that we couldn't get the lamps out very easily. When we did get them out, we took some fine steel wool to them and we haven't had a problem since.
     
  10. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    There really is no long term solution to socket arcing aside from new sockets and new lamps. Even a completely sanded and cleaned socket could suffer from a loss of material and thus contact. Sorry
     
    Last edited: Feb 7, 2013
  11. ship

    ship Senior Team Emeritus Premium Member

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    Specified lamps for this fixture if the 75Q is the BVT, BVV, BVW, & CWZ. Anything other than that removes the UL listing of the lighting fixture. There is also no other lamps available for it in that base type with the same lamp center length.


    It is like a virus. Seemingly from the above, put a good lamp into a bad socket and the lamp goes bad. Later seemingly and no doubt put a bad lamp (the one from the bad socket) into a good new socket, the lamp still goes bad in taking the socket out also now.

    A question of surface conducting contact. The less you have without resistance, the more heat. The more heat, the more oxidation and arching.

    Sanding the lampholder is a concept for resurfacing it but not easy or really correct. Think of it again in the terms of surface area. Light sanding won’t make a smooth surface that allows for even contact across the entire surface of the base normally especially after arching. Heavy sanding often won’t help enough either normally because unless you use a lot of grits in refining and honing that surface back to a mirror smooth finish - without scratches, only those raised non-scratched areas will conduct. Also the entire surface contact plate needs to be in full contact with the button of the lamp. Simply sanding off a bad area would make for a divit.

    After this all is the problem of oxidation of the freshly exposed metal. Same with the base of the lamp itself in cleaning.

    That all said, it is easy to resurface these types of lampholders - I do it a lot professionally and with my antiques. Lots of material on the center contact of a lampholder normally to do so. Gotta be careful, not take off too much, get it even etc.

    Go into details later as to how and with what tools/materials in a reply based off a PM I recently did to someone else on the subject. On the other hand I have also posted about this concept in the past.
     
    lieperjp and (deleted member) like this.
  12. ship

    ship Senior Team Emeritus Premium Member

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    Below is a reply sent to mbangeek about two months ago. It’s not specific to the 8" Fresnel but should be readily adaptable.:

    For starters, the 65Q is only rated for 750w, that could be part of the problem besides just time and age. If you need the output and or want the fake color temperature, and or want to compete with modern Lekos, get the BTH lamp though the lamp life is not that great - more in line with a high output Leko at 300hr, or bring them back down to the BTN 750w lamp.

    Not aware of any 250c cable on the market that will have been used on a Altman fixture. Normally single conductor 250c wire type TGGT is a lot less flexible even as an individual conductor stranded wire and should not be used for a fixture whip. Inside a fixture, fine use it a lot but almost never as a fixture whip.

    More likely it’s a 200c wire, and if original would have been type SF-2 inside a #0 fiberglass sleeving. If multi-conductor, it’s a replacement whip. 15years old I still consider new by the way "TYPE=PICT;ALT="At least that’s post asbestos and they should be grounded.

    Ok, here starts the tacks of what you would want to do/look for.

    First look at the lamps. If really a 1Kw. BTR, they need to be removed and only used on say 10" Altman beam projectors. Otherwise if the theater doesn’t have any of them, see if anyone around has them or on-line has them because they are probably not safe to keep at the school or they will find their way back into the fixtures. Obviously let the TD know this intent. Get them out of the school or destroy the lamps.

    If giving them away, note the condition of the center contact on the lamp. If corroded either clean it by way of a silicone based fiber grinder wheel, nylon based dremmel wheel (below) or buffing wheel w/o compounds to bring it back to bright brass and get it back to flat or rounded instead of arched and or overall pitted. Than treat the center contact with electrical contact cleaner (below). Probably won’t be a problem with the rest of the pre-focus outer (neutral) part of the shell but you could shine it up some also especially with a brass dremmel wheel also (below). Clean the lamp with denatured alcohol - put the alcohol in a small spritz spray bottle, spray on and use a lint free tissue - can probably get a box of it from the photo department or from any camera shop, otherwise raid a first aid kit for some isopropyl alcohol tissues. Wrap the lamp in a second clean tissue tightly once clean and tape it. Than sandwitch or zip lock bag the lamp, mark the bag as clean. Note while cleaning any other condition problems that might necessitate trashing the lamp.

    Next, loosen the cord grip strain relief two screw strain relief. Note while doing so if the strain relief nut loose for later working on it. Unscrew the focus knob and get the lamp/reflector assembly out of the fixture. Take off at least a sampling of the plugs to be aware of how sufficiently or scary the wiring in the plugs is. If one or a few bad, remove all, otherwise if good, tight and in good condition, just observe the rest of the plugs and pull to take apart anything that makes you suspicious.

    Plug operations a different part of the to do list and won’t be covered.

    Lamp out, first check the inside of the socket. Any discoloration - probably? Arching, pitting etc? Check the center spring, should spring as if a spring is retaining it but not a loose spring or a sticky spring. Broken porcelain or really bad gizzards make for spare parts, don’t throw them out yet.

    Take note of the orientation of the pre-focus base. Two cut outs for the pre-focus fins. Is the smaller one towards the reflector or towards the front? Also note the approximate conductor lengths outside of the outer jacket/away from the strain relief. Most likely you will want to reproduce it.

    Next remove the lamp socket from its base - probably stuck, ‘Liquid Wrench spray might help - don’t get it inside the lamp socket, just under the head of the round head 4-40 screw. Could be 6-32 screw but doubtful.

    Note as you remove the screw not so much the screw - unless in really good shape you will be replacing it anyway, brass screws, even normal steel ones don’t like heat than torque and will normally break upon re-install. If in great shape and especially if brass or stainless steel fine. Believe it’s a 4-40x3/8" round head screw (list below) verify the length under the head. Otherwise it’s a new part to buy as with internal tooth lock washers and Locktite #266 or 272 high temp. thread locker. Good idea to take a red sharpee and make the cap of the bottle red so you know which one it is and what specific to use it on or people will use it on stupid stuff.

    Note if the captive nut in the lamp socket is moving about in an other than screw moving type of way as you remove it. Could be a square or even hex nut inside the socket but most likely a nutset inside the porcelain. Cracks to the porcelain about this is bad no matter what type of nut. Cracks anywhere on the porcelain lamp base other than in very few places near where the wiring enters from the bottom would be bad. If near the bottom, can dremmel it smooth again so no sharp edges later. Theoretically possible but not sure what wheel to use. Would need a normal dremmel tool grinding wheel to do so & it will get hot but should work sufficient to get rid of sharp edges.

    Remove the wiring from the socket. Don’t yet attempt to remove the screws completely from it unless the wire is attached by ring terminals, some older lamp sockets don’t have removable screws. If stuck could use electrical contact cleaner on this to help lube it up. Only after the wire is removed, carefully determine by touchy feely if the screw will come completely off the terminal. Many of the older sockets had non-removable screws, remove them and they don’t go back on properly or strip the plate. Most likely yours will come off given the age. If corroded and in bad condition it’s possibly a socket to replace with spare parts, resurface or replace as a socket. Should be a brass 6-32x1/4" slotted pan-head screw but could be the same but 8-32 by up to 5/16" as possible. Again the same thing about breaking easily otherwise in porcelain, screw etc., be careful when removing the screws. If the screw breaks, the plate its attached to possibly can be removed than the screw vise gripped out from the opposing direction, (might want to dremmel grind off the deformed part of the thread on the broken side if this is the case so as to ensure your hole doesn’t get stripped - an on-site determination). Otherwise replaced as a standardized part etc. these plates with spare lamp sockets if removable. Judgement call, extracting by way of drilling out and re-tapping isn’t the best idea overall. Re-tapping once screws are out if they come out if coming out cleanly without going off center or without breaking is a should do on the other hand. Don’t be surprised if the plates these screws are in move about a bit - they normally do. More concerned about the wire to plate screw at the moment and there will be some play.

    Lamp socket free, have a look at the center contact for pitting, arching, corrosion etc. as with the shell for discoloration and worse. Center contact should push in and out as said and also might screw tighter or looser the tension on the center contact - dependant on which brand. Could also screw tighter to the bottom hot contact plate. Should rotate some and push in and come back without a problem.

    Next step assuming a socket that is not cracked in a bad way would be to clean it up - assuming not too much else wrong with it. 15 years old, it will probably be good for servicing and won’t have as many difficulties really old Bryant or especially GE bases would. Take a 1/8" tip slotted screw driver and screw down tight the outer neutral shell. Don’t attempt to take apart the lamp socket - normally it’s mechanically fine and don’t go back together that well. If you want you can add ht thread locker to the non-contact plate threaded side of the shell but other than that don’t take it apart unless scrapping it for spare parts. First the brass wire dremmel wheel on the outer shell. Get under the ridges of the pre-focus and as deep as reasonable without having to get all the way down. Should clean it up well short of some stain or pitting that might need a nylon fiber wheel or possibly can be ignored. Next the center contact that’s normally the worst. Judgement call if it can be serviced or not. Depends on how thin the material is and how much material has welded to it, or how pitted it is. Normally a combination of nylon fiber wheels between coarse and fine should be able to resurface the center contact without a problem. Smooth and flat or smooth with a center recess. Limited pits - don’t try to grind down too hard on them, just level them out and determine if the pits are too deep or for good electrical contact or not. Very much a judgement call on when to replace the socket. Flip over and surface as needed with wire wheel and fiber tip the wire / screw contact plates. Once all clean, all screws possible (normally center contact plate screw not possible to tighten) tight, spray down all surfaces with electrical contact cleaner and let drip dry. No, not persay rated for the heat but I have been using it on 5Kw Fresnels and larger for years with out a problem, it will take the heat.

    If you need to replace the socket, keep in mind that many brands of modern sockets are a bit larger. Should still fit in the bracket and holes should align but it’s going to be bigger & you might have to move the grounding screw.. Also, some brands won’t have side wireway holes cut out in them and should be returned if not. Good option if replacing sockets would be ones with say 30" or 42" whips already on them in saving time and money plus effort. Still should follow the silicone coated fiberglass over sleeving note below on them and other attachment notes but otherwise highly recommended.

    Under the socket should have been some type of insulator padding. Trash it its’ going to be bad. Next check the ground wire connection that should be on the lamp socket carriage. Rivet loose in wire being able to move? Wire in good shape? Often this will be a type FEP w/o fiberglass insulation on it. If loose, could pound the rivet tight again or cut the ground, drill out and replace with #10 ring terminal (doesn’t have to be high temp. but should not be insulated - pull the insulation off if needed), 10-32x1/2" slotted hex washer head green ground screw, external tooth lock washer and #10-32 top lock 18-8 stainless steel top lock nut. Good combination for doing a ground. Often I’ll use one lock washer under the nut and one bet. Screw and ring terminal or under it if painted surface.

    For above wire, most cable distribution companies should have it or theater suppliers or email McMaster Carr or others and they can get it or define further what they have in part number for compliance. Need black and white 200c fiberglass insulated Teflon or silicone 19 strand SF-2 and green the same or 200c to 150c FEP / type K insulated wire.

    Than fiberglass sleeving - either normal #0 size fiberglass or vinyl coated #0 fiberglass sleeving for more abrasion resistance. Again, above types of suppliers or McMaster Carr.

    Ready to crimp? Need a tooth Klien/Stakon #1005 single jaw type crimp tool especially on high-temp crimp terminals to properly crimp them, than give them a hard tug to ensure it’s tight enough. This is the proper tool for this gauge of wire. Don’t forget to put the saddle of the crimp tool into the seam of the crimp part of the ring terminal. Jaw of the tool goes into somewhere that ain’t a seam or it won’t be a proper crimp. Below is the high temp crimp terminal type, make sure the ring terminal matches up with the size of screw on the lamp socket. Possible it’s a 8-32 instead which would require a different size ring terminal. Parts list below. First before buying wire, normally on wire what gets melted or burned up is only the first inch or so, cut it off and re-use the whip possible? Might need to replace the fiberglass over sleeving if stranded conductors inside but otherwise might only be necessary to replace a inch or so of the told about multi-conductor wiring as long as otherwise in good shape. Look for a high temp. wire SF-2 that’s fiberglass sleeved on each of the conductors if doing replacement. The other high temp stuff even if called SF-2 (teflon/silicone don’t matter) without the sleeving is rated for as much and you could use it but it don’t last as well near the source of heat. You mention 14/3 type, multi conductor. Is it “rockbestos” brand name? Normally 200c. Good as gold in also cutting a bit, stripping a bit of the outer jacket and re-crimping. If silicone especially by Lex, be suspicious - silicone euro style heat wire don’t take well to nuthing and cuts down to copper with a finger nail. That’s what Altman switched to a few years ago. Could still use it and it’s UL listed, just be careful of DF-50 fluid exposure to it and cuts. TMB makes a better silicone multi-conductor and even a better jacketed version much like the famed “Rockbestos” now discontinued..

    So either individual conductors in fiberglass or vinyl coated sleeving- this especially if new lamp sockets with whips already on them, or if servicable the multi-conductor or sleeved whips already on them cut back some, or the TMB stuff. Crimp the high temp. ring terminals on the conductors. Don’t have to do high temp for the ground and also note it’s a different stud/screw size. Really can just go to the store and buy a insulated 14-16ga #10 vinyl insulated (blue) ring terminal and pull off the vinyl insulation. Note the hot / black center from the shell neutral / white. If the conductors are not marked, sharpee in a black stripe to the black - it matters. If Euro, blue is neutral, brown is hot.

    On the barrel of the crimp do three layers of #27 Scotch fiberglass electrical tape with some overlap onto the wire and sleeve the first at least 3" of the wire near the crimp with #12 silicone coated fiberglass sleeving. Cover your crimp also with it if possible. Don’t need to tape the sleeving in place, should stay where it is but if you do, do so near the top not under the socket at the crimp or it would now become too much stuff under the socket and probably break the porcelain as you tighten it, just slide it all the way down. This will provide some extra insulation against abrasion, sharp edges and heat.

    Following treating the resurfaced or replaced and re-tapped for terminal base, get the new brass screws or re-use the old ones dependant on oxidation on them as an indication of what kind of shape and conductivity they are in. Add a silicone bronze lock washer to them. Screw the wire to the base, add some high temp. threadlocker to the 4-40 screws, (no thread locker on any screws that conduct electricity) add a internal tooth lock washer and re-attach to the base slide assembly. Before doing so, you need to add a ceramic fiber insulator pad between the socket and slide plate. Cut some 1/16" fiber padding a little bigger than the socket or use a 1/16" Teflon pad cut and drilled to match the silicone circuit board like ones that come with new sockets if the fixture might get moist. Never used a Teflon insulator pad other than for 2K scoops, but it should work fine. Ceramic fiber pads otherwise work well. If courtous, write on the ceramic fiber pad “not asbestos” so those in the future don’t worry. Mounting screws should break their way thru the insulator padding - very important. Can use the padding plate that comes with a new lamp socket otherwise but they don’t take heat as well. Very important this insulator.

    Take off the reflector, judge it’s condition. If cloudy, it’s possible with some work to clean it. If crackly, probably needs replacement. If cloudy get out some felt or cotton pads for the Dremmel tool and with rubbing compound if really bad or just Maaz metal polish (can provide mcmaster part number later if needed) proceed to buff the heck out of the reflector. Should get the clouds out. If not too bad, can just dish washer it and or use a good window washing compound. Follow up by another cleaning with polish and rag as needed, than window washing compound, than a spraying and cleaning with denatured alcohol and rag to remove any residue. Should get a nice and clean reflector. Re-attach as normal, perhaps add lock washer and or replace screws on it. Make sure the reflector is perpendicular to the base of the slide plate. If other than and older than Altman 65Q some reflectors will have a deeper concave than others, and also some will be blackened around the flange of the reflector so as to better control stray light. Touching up the black with high temp. paint can be useful, what brand or type reflector in the end is used most likely won’t matter, not efficient enough. Clean the rear of the reflector also and while around the back of it, if you see a matt or whitened part of it often bubbling up, time to replace the reflector in the heat melting thru it.

    Clean the front lens - carful not to chip it as you remove the front lens. Dish washers with Jet Dry works great, especially industrial dish washers. Also works for reflectors if not cloudy. Don’t worry about coatings, not on it or the anodized coating on the reflector won’t wear off by washing. Otherwise the window cleaning solution followed by the denatured alcohol.
    Pay attention to the lens retaining ring. Possibly a good time to send it thru a wire wheel than get a wipe down with a rag soaked with say WD-40. Careful again not to chip the lens while working with a confounded lens retaining ring - especially if old style without the fingers to it. Check the tension on the ring - should be tight enough that if you can remove it with your fingers, it should be really hard to do so otherwise replace it.

    Next the slide plate(s) under the lamp base assembly. Clean it up well with a general surface cleaner or window wash cleaner first. Than judge if paint peeling bent edge, center concaving out etc. needing to be pounded back to shape or paint scraped off if paint on it. Once clean, denatured alcohol off the residue from the cleaner and I like to use spray graphite to treat this surface for heat and glide. Dri Slide is good as spray graphite but anything will work including the spray graphite designed for key locks. Different than the powder stuff in how it gets applied/sticks. Wipe off the excess after the vehicle has dripped or dried off it.

    Also like to remove all screws/bolts/knobs at this point and tap/die them at this point, replace what’s warn or rusting and oil them up or thead locker them up. If the lamp assembly focus knob is missing its washer, good time to add one also. Not always on them but a good thing to add if not. This service/replacement also for the cord grip strain relief with threadlocker and tightening. If old style knob w/o clutch ring or thermoplastic handle, pay special attention to it. If your cord grip strain relief is loose, remove it and add thread locker to its nut. Also if your strain relief seems to be rough cast in having sharp edges to the strap or cating wire wheel them some before re-installing. Be careful when re-installing not to break it - easily done. Of your yoke knobs, if old style - before yoke clutches, run them thru a die in removing any excess cast aluminum getting in the way of properly screwing it down etc, or replace with a new handle if the set screw inside the casting looks like its ready to pop. Cone washers should also be in good shape - normally are or replaced. As with plugs the C-Clamp service call is another project in itself but normally I check for bent clamps, re-tap and oil it up etc.

    Check the fixture, paint in good shape? Spot welds not rusting out or popping? Re-paint needed after a sand blasting or chipping and wire brushing? Yoke need some paint/pounding? Make sure if you paint to blue masking tape over any factory stickers or plates, than promptly remove the tape. Very important to keep the labeling on the fixture.


    Feed the fixture whip back into the strain relief, focus the fixture in flood, allow a wee bit of slack and mark where the whip wants to sit in the strain relief. Focus/spot the fixture a few times in excercising the wire feeding the lamp socket and bring back to spot position. Mark on the outside of the fixture whip where the cable is at, pull out the slack and add three or a few more layers of fiberglass electrical tape 1" outside the strain relief and directly under where it will want to clamp. This will serve two purposes. First at the strain relief, help to prevent the clamp from cutting into the cable. Second prevent too much flex directly at the clamp for the cable which could harm the cable and jacket. Bring back to flood and adjust the whip, tighten down the strain relief screws and go back to flood/spot adjustments to ensure it’s working right and the wire is trained to fold without fouling.
    Button up and dog down screws, play with the focus more, - might take some pushing on the reflector assembly to train the wire in focus assembly going from spot to focus. Fixture might not want to go full absolute spot focus which is ok in some cases, or an adjustment might be needed. Take a flash light and make sure your conductors are not going to get hung up on anything, rub against surfaces as they focus etc. No glide plates snagging the wires, housing bottom rubbing wires as they slide etc.

    Finally, good time to stencil the theater’s letters on the yoke and make sure the safety cable is there if not slung around the yoke and in good condition.

    Think that about covers it. The 6-32 screw up front that holds the lens assembly on and acts like a hinge. Forget... 6-32 or 8-32. Darned acorn nuts. Too tight they are binding the metal? Too loose and need thread locker? Rusted solid? Can replace with normal screw and nylock nut if needed - a wee bit long one but normal, perhaps stainless steel would be a better hinge point otherwise but them acorn nuts - make sure they are in good shape if not replaced with nylock. Top lens retainer screwd in and not coming loose from its spring plate? Not bent out of shape etc? Service call.

    Blow out the fixture really well before putting the lamp in. Perhaps clean it with the window washing compound as needed.





    Below McMaster Carr part numbers if of help: (verify description above and below matches part number before ordering. Could be off a part number / size or two at times and probably am in some instances - done quickly but should get you into the proper chart)

    single jaw crimp tool #7289k1
    nylon mesh flat or round tip abrasive tip 4630a14 or 4630a19 - specify fine and course tip
    nylon mesh cone abrasive tip 4630a13 - specify fine and course tips
    1" brass wire wheel 4792a22
    1/4" brass wire wheel 4792a32 (that’s not correct, check 2 pages before) 1/8" shank like 3/8" bristle.
    3M Scotch #27 fiberglass electrical tape, ½" 76455a17
    High temp 14-16ga #6 stud ring terminal 69405k15
    #12 silicone coated fiberglass sleeving 7453k83
    10-32x3/8" ground screw 92597a400
    10-32 s.steel top lock nut 90045a18
    #10 external tooth lock washer, zinc 91114a011
    #6 silicone bronze external tooth washer 92164a009
    #4 s.steel internal tooth lock washer 91757a101
    2x 4-40x3/8" slotted 18-8 s.steel round head screw 91810a108
    1x Locktite #266 high temp. (red) thread locker
    1x Electrical Contact Cleaner w. Lubricant Skotchkote Electrical Coating, 15oz. can #7437k15
    2x 6-32x1/4" brass pan-head screw 92446a1441/32"x3"x50' Ceramic Fiber Strip 87575K83 (use the 1/16" size)
    Graphite Dry Lubricant Aerosol 20F-+850F, 10oz Aerosol 13725k12
    Dry Slide Moly Lubricant 5.1/2oz Aerosol, Corrosion Resistor 1163k12
    Rust-Stopper Aerosol Paint Self-Priming, Gloss Black, 12 oz Net Wt 77025T731
    Flat Black Tough-Coat Rust-Stopper Aerosol Paint 15 Ounce Net Weight 7891T3
    Engine Aerosol Paint Gloss Universal Black, 11 Ounce Net Weight 7614T418
    High-Temperature Aerosol Paint Flat Black,, 12 oz 7832T19
    Polyester/Cellulose Clean Room Wipe 4" X 4", Packs of 300 7089T31
     
    Last edited: Feb 5, 2009
  13. lieperjp

    lieperjp Well-Known Member

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    Ship, you never cease to amaze me.
     
  14. AdamC

    AdamC Member

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    Baltimore, MD
    I'm resurrecting this old thread to ask if there's a better / cheaper way to deal with the arced sockets in our Fresnels.

    We have a bunch of 65Qs with 750W BTN lamps in them, and replacing the medium prefocus sockets (and the arced lamps) is getting pretty expensive. We never use the arced lamps or sockets, but the arcing happens pretty frequently even with new lamps and new sockets. The price for the sockets has gone from $13 to $19 in the last year, and it just seems wasteful to replace the entire socket when it appears that the only bad parts are the center contact and the spring.

    We now have a bunch of used sockets that have arced & oxidized center contacts, and springs that are weak from overheating. The other parts of the sockets seem to be fine. Since the center contact can unscrew, and because it's very thick, I'm wondering if I could polish away the oxidization, and replace the spring, to repair these sockets? Is there a good place to buy a suitable spring, that can handle the heat, and is at least as strong as the original? Stronger would be better, since I suspect weak springs are causing this problem in the first place. I'm not really sure how to spec the spring...

    Has anyone tried this? Do you think it would work?

    Thanks!
    Adam
     
  15. ship

    ship Senior Team Emeritus Premium Member

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    Do Mog. Prefocus bases really sell for that much? Wow.

    Resurfacing with Dremmel tool with various Silicone abrasive bits than contact cleaner to the base tends to work well often in lots of resurfacing area for such a base to be reconditioned on before the need to replace. This assuming a new lamp now installed into the fixture or at last also a resurfaced used lamp in not transferring as above mentioned the disease as it were of bad lamp to new base.

    McMaster.com amongst many suppliers, find a similar product to their #4630A143 fine grit Nylon Mesh Abrasive Shank-Mount Bit Shape B90, 1/2" Dia, Silicon Carbide, dremmel tool bit.

    Start with say a medium grit within the section than finish with fine grit. Really good for re-surfacing the center contact. After that, a brass whire wheel for the Dremmel often can clean off any corrosion to the outer shell. Most often if you don't get too ambitious or the base is not too far gone you can do a really good job of resurfacing above what sand paper will do and leave scratches in doing so.

    Once smooth or at least with a few pock marks but mostly able to conduct with a smooth surface both to lamp and base, I use McMaster part number 7437k15 Electrical Contact Cleaner w. Lubericant 16oz. Spray on the surfaces re-finished in up to 5Kw lamps. Works well though its rating is not for such temperatures. Possibly also depends upon how refined a finish you have done to the base or how far gone it was in resurfacing and getting it flat again.

    Still though as a concept a few grades of silicone fiber Dremmel wheels and a coating and normally the base is fine. Lamp... depends on cleaning of it and how abused it was in the long run.

    On lamps, the BVT is probably the most efficient for the fixture. Sorry, no upgraded longer life or 115v high output versions soon in coming. Downsizing to the P-28s would probably be easy enough but also not really a good idea to put time into. Upgraded or better lamps could work once retrofitted but you do get that blocked up base that now blocks the Fresnel proper beam spread in doing so.

    Possible to upgrade to better lamp etc.. sure and could be done but its an 8" Fresnel and it for the most part works fine how it is once in proper operating condition.
     
  16. CRDunham

    CRDunham Member

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    I've had some luck using a conductive grease (available from McMaster-Carr) to reduce arcing in my crappy fresnels. Enough so that I'm going to start using it preventatively once I replace the sockets. Arcing IS a slippery slope.
     
  17. ptero

    ptero Active Member

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    Just a minor addition to the previous comments. Sanding the socket center contact works to a point, but is not a great solution.

    Part of the issue with our old gear is the spring under that center contact that provides pressure against the lamp bottom. With age it becomes weaker and accelerates the arcing problem. That's all I got. :cool:
     
  18. ship

    ship Senior Team Emeritus Premium Member

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    Never really found much of a problem of weakened springs under the center contact. (I have resurfaced literally hundreds of Fresnel bases in the past). One would think with heat they would temper more and become harder in also conducting less, if not break with the testing of it’s tension more so than become more springie and weaker with contact towards its optimum compression. Possible. Granted I have seen some really springie bases in the past and adjusting tension some on those bases that could be adjusted did seem to fix this problem of similarity some and perhaps if possible it is a solution. This all given the weaker spring, seating a lamp doesn’t make for more tension from compression - it stays the same, but perhaps what tension is noted is starting tension but what the lamp sees when seated is proper.

    Possible a weak spring could cause lamps to go bad with less tension overall, but I don’t think it feasible in this case as it is touching and even with a weak spring should still be providing a good enough touch to conduct. On a 5K Fresnel sure, spring tension is needed if not what I prefer, clamped tension. On the other hand, think of a stage pin plug - there is no real tension there, just surface contact, and it is sufficient to conduct up to 100A w/o tension of a spring.

    The spring under the center contact I think less important for other than retaining the lamp for the upper fins return. Springie I think fine for the most part. Too hard and it could become a problem instead.

    Believe I’m aware of three types of center button ends to P-28s lamps. Old solder button is I think perhaps the worst in melting, arching and pitting overall shown after time. With heat also the solder can melt or move about around the lead in wire and cause failure or higher resistance. Equal to this or perhaps worse is the rounded off bullet tipped base center contact such as one might find on a EVR lamp. This nickel plated tipped lamp type while good in that it cannot melt around the surface has a much smaller surface area and tends to indent the base contact of the base - especially with a harder spring. Such a small contact area in passing the current of the lamp does perhaps get hotter. Such a small area of contact also will tend to overheat in that area worse in while the base plate might look good, where the actual contact is might be very high resistance by way of heat damage in a way that’s really hard to fix like a pitted area that cannot be buffed out. Cannot buff out an indent from a pin touching the base as easily.

    Best type of base to a Fresnel lamp I think is a brass or better yet nickel plated center contact button that is like 3/8" dia. You no longer have the problems of solder in melting or not being even or melting and conforming, and you have more surface area in contact with the button. The non-treated brass button doesn’t take heat as well but can be shined up, the nickel plated one shouldn’t go bad unless you have a base problem.

    Could be that the brand of lamps could be contributing to the problem. Just a thought and concept. I’m sure the various lamp manufacturers could tell different than these above observations but I think such concepts could help be a further cause of bad bases, this over bad weak springs..
     

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