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Made by Monkeys

Poor Lamp Socket Design Sparks Danger

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Jon Titus
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Re: LAMP SOCKETS, etal....
Jon Titus   4/23/2012 6:54:46 PM
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Good to know, Larry.  Thankfully I found a good quality socket, but I also have some 2-56 hardware handy, too.

Larry M
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Re: LAMP SOCKETS, etal....
Larry M   4/23/2012 10:36:08 AM
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Jon Titus wrote: " I also thought about running a 2-56 bolt through the brass tubing, tightening it and locking it in place. I might do that if I can't find an Eagle or Leviton replacement with a solid connection. We'll see..."

 

Jon, I've done this. I had to drill through the rivet, thinning it's walls, for the 2-56 machine screw to clear. The repair was easy and successful.

Jon Titus
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Re: new vs old
Jon Titus   4/12/2012 5:29:17 PM
Yes, aluminum has a higher resistivity than copper, but the resistance overall is so low compared to the load resistance that you lose an insignificant amount of energy in either type of wire. Instead of WD-40, try the silicone grease I recommended in an earlier blog post.  WD-40 is a water displacement agent used to help prevent corrosion.

Tool_maker
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new vs old
Tool_maker   4/12/2012 4:56:02 PM
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I read so many posts in this publication about the failures of new elecric devices that I have to wonder if any manufacturer knows how to make reliable electrics today. I am a fan of estate sales and have a great deal of luck with refurbishing old stuff.

On the aluminum wiring, I heard years ago that it has a higher resistance than copper, so powering the exact same devices in a house with aluminum wire will cost more than if the wire is copper. Does anyone know if that is correct?

I also replace all "bulb down sockets" with pocelain. Ceiling fans for example and put a drop of WD 40 on aluminum light bulb bases. It seems to make bulbs easier to change.

Bernie
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Iron
Poor lamp socket design
Bernie   4/11/2012 3:28:48 PM
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Toward the end of the 1960's, aluminum was used for house wiring.  There were fires, initially in travel homes, but later, regular homes also experienced fires.  The cause was aluminum wires.  Aluminum has two properties that caused this problem.  First, it is a soft metal, and second, its oxide is a tough film, and an insulator.  In the case of the home wiring, vibration in mobile homes during delivery or driving, loosened the screws in the receptacle and socket contacts.  This was followed by oxidation and a reduction in the contact area because some of it was oxidized and became an insulator.  The result was heating at the contacts.

A similar problem arose with stationary homes.  Here, since the aluminum wires were softer than the brass contacts, if the wires at the contacts heated enough, the aluminum would deform because of the restriction of the contact screws.  When the contact cooled, the aluminum would contract and now there would be space where the aluminum could oxidize.

It is possible that this mechanism was the cause of the failed socket.

Jon Titus
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Re: LAMP SOCKETS, etal....
Jon Titus   4/11/2012 11:53:56 AM
Even aluminum-on-aluminum sockets can have problems, so i always put a thin coat of high-temperature silicone vacuum grease on threads before I screw in a new bulb.  I use Dow-Corning "High Vacuum Grease." The price ranges from about $20 to $32 for a 150-gram tube, but it will last for several generations.  I also use this grease on outdoor electrical and RF connectors to provide additional water resistance.

OldGeek
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Re: LAMP SOCKETS, etal....
OldGeek   4/11/2012 11:42:06 AM
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Jon, I think you're dead on about the need for an update in socket design. I'm also pretty sure it won't happen any time soon just because of the enormous number of installed sockets. If a good design comes forward that could be easily fitted to existing sockets by using a screw in adapter it would have a much better chance.

Your particular problem is primarily because of the 3-way design. In the standard base, the rivets don't have to remain tight because the spring on the center contact keeps them held against the socket shell. Because the third contact of your socket is solid, the only thing holding the rivet tight is the springiness of the socket shell and that doesn't have enough "give" to be much help. If you can't find a socket with a spring third contact the addition of a screw might be your best shot, especially if you add a spring lock washer.

While a brass socket shell SOUNDS like a good idea, it has one major flaw: all modern light bulbs have an aluminum base. Brass sockets went out of favor soon after bulb bases changed to aluminum, probably because electrolytic corrosion started cementing bulbs into sockets.

Best of luck in your quest for the perfect socket :-)

 

Jon Titus
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How many wires in a box?
Jon Titus   4/11/2012 11:38:36 AM
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Hi, OLD_CURMUDGEON.  The electrical code specifies a certain size box given the number and gauges of wires in the box. So if you overstuff a box, your work won't pass inspection. Boxes should have their volume clearly marked and a calculation yields the volume needed for the wires.  Fine Homebuilding magazine ran an article that includes an example: http://www.finehomebuilding.com/how-to/articles/more-wires-need-bigger-boxes.aspx.

Dave Palmer
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Platinum
Re: Lamp socket construction sparks danger.
Dave Palmer   4/11/2012 10:32:27 AM
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@RNDDUDE: I agree with you; the root cause of the problem in the lamp story seems likely to be galvanic corrosion between the aluminum sleeve and the copper tube.  It doesn't help that copper is at the top of the galvanic series and aluminum is at the bottom.  They just don't play well together.

bob from maine
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Platinum
Lamp Socket Sparks Danger
bob from maine   4/11/2012 10:23:08 AM
The current path on those sockets is thru the rivet to the aluminum outer sleeve which makes contact with the threads on the bulb. The rivet to wire type of connection is also used in UL approved mechanism's such as electric motor starter circuits that use a printed circuit board. Once any resistance develops, heat follows, with hundred or thousands of cycles, eventually the resistance gets high enough to cause enough heat to carbonize the supporting plastic and restistance increases, etc. etc.. General Electric made a series of hot water circulating pumps used on furnaces from the 50's to at least the 90's and they had a brass rivet holding a crimped wire terminal against the printed circuit board. Once a little oxidation appeared the resistance went up and each time the motor started, a small arc would occur. Eventually this arc would cause the epoxy board to decompose and the contact would become intermittent. It was a real difficult problem to locate and the solution required replacing a $115 motor because the $1.50 circuit board wasn't available. Using this type of termination for components is not all that uncommon, even today.

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