my profile | my password | search | faq & rules | forum home

» Film-Tech Forum ARCHIVE   » Operations   » Film Handlers' Forum   » Cleaning silver contacts in a carbon arc lamphouse

Author Topic: Cleaning silver contacts in a carbon arc lamphouse William Hooper Phenomenal Film Handler Posts: 1879 From: Mobile, AL USA Registered: Jun 99 posted 09-15-2003 03:58 AM                        There are some areas of tarnish on the silver contacts in a lamphouse that I just can't get rid of. What recommendations are there for cleaning them completely?  |  IP: Logged John Pytlak Film God Posts: 9987 From: Rochester, NY 14650-1922 Registered: Jan 2000 posted 09-15-2003 08:22 AM                        Does the tarnish cause a problem with the electrical contact, or is it just an "appearance" issue? When I worked at the drive-in, we just used a round stiff-bristled "bottle" brush daily to clean the inside of the contacts where the carbon rotated.  |  IP: Logged William H. Ward Film Handler Posts: 27 From: SAn Antonio, Texas Registered: Jul 2003 posted 09-15-2003 10:32 AM                     Oops, made a mistake. See my new post "cleaning contacts." Should have been a relpy instead of a new post..... --- When I was a booth operator, cleaning contacts was a daily per shift requirement. For Strong rotating lamps, we used just a brush (tubular). Oxides of carbon, which was the residue seen, were good conductors and posed no problems. Ashcraft lamp silver contacts were cleaned with powdered Bon Ami. On your cloth, work up a good paste, scrub, let dry and polish it off. We used the same stuff on reflectors. Worked great. [ 09-15-2003, 01:56 PM: Message edited by: Daryl C. W. O'Shea ]  |  IP: Logged Jim Spohn Film Handler Posts: 95 From: Bakersfield, CA, USA Registered: Jan 2003 posted 09-15-2003 10:54 AM                     John is right on the money! If the blemishes are tarnished black, then they are silver oxcide (which is a better conductor than silver) don't worry about them. However if the marks on the contacts are burned and pitted, the only thing you can do is remove material until things are flat again. Filing out the contacts can be done if EXTREEMLY careful not to go too far. once the contacts get too thin they: A) Won't make good contact B) Won't dissapate the heat well. For the most part if the contacts are working ok but just look crappy, leave them alone. I screwed up and cleaned mine with a file and improved them to the point that they were totally useless (I'm learning). I ended up casting new ones from coin silver and machining. Good luck  |  IP: Logged Dick Prather Master Film Handler Posts: 259 From: Portland, OR, USA Registered: Feb 2002 posted 09-15-2003 04:47 PM                     As stated above I used to use a round stiff bristle brush every day as part of routine lamp cleaning. We used Bon-Ami every couple of months or only when needed. The main thing we did was wipe the dust off the carbon with a small towel everytime we put a new stick in. The dust acts like a fine gringing compound on the silver contacts. That really helped prolong the contacts. I got the hint from a senior operator at one of the first run houses and it seemed to work great. The regular operator had been using Bon-Ami daily and we he went through contacts once or twice a year. After using the brush and wiping the carbon we went to almost no changes in the six years I was there at the DI.  |  IP: Logged William Hooper Phenomenal Film Handler Posts: 1879 From: Mobile, AL USA Registered: Jun 99 posted 09-16-2003 12:16 AM                        Thanks everyone! It's a black, tarnished area inside the contacts which is not removed when polishing with Comet paste on a wet cloth, so I assume it is a pitted area. These areas are mostly scratch-like, elongated in the direction of the carbon rod, so that looks like it jibes with Dick Prather's information about dust on the carbon acting as an abrasive - they could have begun as scores from carbons being slid in. I guess dealing with the tarnish which can't be removed would be decided by whether silver oxide accelerates deterioration of the rest of the silver beneath it, or will it like aluminum oxide prevent it? The theater does not show films all the time - they'll run for consecutive weekends for a while, then not run any for a month, then run a matinee & midnight movie one weekend, etc., so "routine maintenance" is usually a new routine that must be devised.  |  IP: Logged Robert Throop Master Film Handler Posts: 412 From: Vernon, NY USA Registered: Jun 99 posted 09-16-2003 05:26 PM                     I worked in a house that had Super Core Lites. We cleaned the contacts daily with Bon Ami which is the recommended method in the Ashcraft manual. The first set of contacts lasted at least ten years.  |  IP: Logged Edward Jurich Master Film Handler Posts: 305 From: Las Vegas USA Registered: Jul 2003 posted 09-16-2003 08:37 PM                     Hey Bill, you can resilver bad areas. Check and see what's used in transmitter re-slivering, Geoff might be able to get that info for you.  |  IP: Logged Gerard S. Cohen Jedi Master Film Handler Posts: 975 From: Forest Hills, NY, USA Registered: Sep 2001 posted 09-16-2003 08:59 PM                     I've only had very limited experience with those beautiful Ashcraft lamphouses with revolving, silver, chain-driven positive carbon jaws. So permit me to ask, "Are the 'silver' jaws real silver, or, like the positive carbon posts in the Peerless Magnarc lamps, made of so called German silver? German silver is not silver, but a nickel alloy also called monel metal or alpaca. It resists tarnishing and was often used in Europe for cookware and eating utensils, as it gleams and resists corrosion, yet transmits heat well. It must also be a good conductor of electricity. So which was used for Ashcraft jaws?  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-16-2003 09:44 PM                     They are reel silver  |  IP: Logged William Hooper Phenomenal Film Handler Posts: 1879 From: Mobile, AL USA Registered: Jun 99 posted 09-17-2003 12:21 AM                        These are Ashcraft Core-Lites, with revolving positives. #1's contacts seem to be sort of non-standard, almost like they were whittled from a chunk of solid silver. #2 has an "11mm" factory-looking stamp on them. #2's also have a spot near the back where it looks like the negative collided with them (the negative was somehow in crooked?), & are slightly melted. There are a few sort of golden, brass-looking spots there. Ed: Great tip!  |  IP: Logged John T. Mellor Film Handler Posts: 52 From: Htafield, Pennsylvania, USA Registered: May 2000 posted 09-17-2003 09:19 PM                     We always used Bon Ami when it was time to do a real good cleaning . but we also cleaned them every day to get rid of the dust . We also used to put the next few days rods in the lamphouse to make sure they were dried out. [one of my old employers bought Le Arto carbons ]if you know about them you know why we cooked them befotre we used them. I ran a lot of Ashcraft 13.6 mm , but the best was the Perless Hy-candescent ,if you know about them then you worked a great lamphouse. P.S. I still have a set [1] 13.6 mm Ashcraft contacts never ben used  |  IP: Logged

All times are Central (GMT -6:00)

Printer-friendly view of this topic

Hop To: Select a Forum: Category: Operations -------------------- Digital Cinema Forum Film Handlers' Forum Large Format Forum Ground Level Feature Info, Trailer Attachments & REAL Credit Offsets Category: Community -------------------- Film-Yak Film Handlers' Movie Reviews The Afterlife Bob Maar's Joke-A-Thon Category: Classified -------------------- Equipment and Supplies Wanted/For Sale Help Wanted/Seeking Employment Category: System -------------------- Software Beta Testing Forum

The Film-Tech Forums are designed for various members related to the cinema industry to express their opinions, viewpoints and testimonials on various products, services and events based upon speculation, personal knowledge and factual information through use, therefore all views represented here allow no liability upon the publishers of this web site and the owners of said views assume no liability for any ill will resulting from these postings. The posts made here are for educational as well as entertainment purposes and as such anyone viewing this portion of the website must accept these views as statements of the author of that opinion and agrees to release the authors from any and all liability.