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Poor Lamp Socket Design Sparks Danger
4/10/2012

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Mydesign
User Rank
Platinum
Design Flaws
Mydesign   4/10/2012 6:06:06 AM
Jon, quality and finishing matters a lot, especially anything related to electricity. It's not safe to handle any devices made of poor quality materials, which can end up in electric shock. Proper design to handle the device is also important.

naperlou
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Blogger
Re: Design Flaws
naperlou   4/10/2012 10:08:18 AM
NO RATINGS
Jon is correct.  You really need to look for the UL, or similar, testing labels.  Cheap parts are nice in that they keep the price of products down.  On the other hand, as Mydesign points out it can be dangerous if you are dealing with electricity.

As for an new design for lightbulbs, the reason this has not been changed is that the manufacturers don't want to force the cost of an upgrade on the consumer.  This is nice, but it also perpetuates poor design choices of the past.

TJ McDermott
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Blogger
Re: Design Flaws
TJ McDermott   4/10/2012 10:17:23 AM
Naperlou, the independent party testing label is still not a guarantee of a good design, or even of a valid part.  UL is constantly watching out for parts with counterfeited labels.  The parts most commonly seen with such false labels come from overseas because it is difficult to prosecute.

Jon Titus
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Blogger
Re: Design Flaws
Jon Titus   4/10/2012 10:47:32 AM
Good point, TJ.  We have counterfeit semiconductors imported from Asia, so it's no big deal to put a UL or CSA label on a component such as a light socket, particularly if purchasing and manufacturing occur somewhere in Asia. And it's not just counterfeiting of electrical and electronic materials. The FDA has many cases of fake drugs--Avastin, for example--coming from overseas "suppliers."  In the case of Avastin, the source of the fake drug didn't even bother tp try to reproduce the type of label Genentech puts on the real drug and it still got through several distributors.

Ann R. Thryft
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Blogger
Re: Design Flaws
Ann R. Thryft   4/10/2012 1:08:23 PM

Jon, thanks for this article and even more for your comment about counterfeit UL labels. How scary is that?! I knew about fake chips and drugs, but fake electrical compliance labels is something we can't "watch out for" as consumers--how the heck are we supposed to know they are fake?


OLD_CURMUDGEON
User Rank
Platinum
LAMP SOCKETS, etal....
OLD_CURMUDGEON   4/10/2012 3:19:18 PM
There's probably ONLY two manufacturers of these devices left in the U.S. / Canada, and that's LEVITON & EAGLE.  You know that even IF they manufacture some items in China, they have rigid quslity control procedures in place to prevent such anomalies.

Jon touched on the very essence of the problem with this socket.  An aluminum shell with brass rivets.  That's the same lethal combination that was present in the late 1960s when copper was scarce due to the Viet Nam conflict, and houses were being built using aluminum wiring.  Even the revised copper-clad aluminum wiring still posed a potential threat.  IF you did any electrical work during that period, you learned very quickly to bathe the terminals in "NO-ALOX", or another anti-oxidizing compound to inhibit the formation of Al Oxide.  And, terminals on devices were relabeled w/ the CU/AL logo to identify them as safe for either copper wire, copper-clad wire, OR aluminum wire.

Rob Spiegel
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Blogger
Re: Design Flaws
Rob Spiegel   4/10/2012 4:02:39 PM

Not sure how drugs are examined to identify counterfeit, but the Independent Distributors of Electronics Association offers certification in identifying counterfeit electronic components. Apparently there are signs to help inspectors identify counterfeit components even though the counterfeiters are getting very clever (such as having legitimate components sitting on top of counterfeit components).

oldguywithtoys
User Rank
Silver
It can happen with U.S. parts, too.
oldguywithtoys   4/10/2012 4:04:27 PM
NO RATINGS
I'm convinced it's the difference in the thermal coefficient of expansion between the brass rivet and the aluminum shell.  I've replaced several Edison sockets over the years. Though the ones in the little 150W PAR cans I use in a small stage-lighting rig are ceramic rather than phenolic, the construction is similar.  Over the years I've had a couple of the replacements (from a U.S. manufacturer) fail as well, always with the same problem.  But I'm old enough to remember Edison sockets with identical construction except that the shell was also a brass, bronze or copper alloy, not aluminum.  I don't recall seeing this particular failure mode back then.

Jon Titus
User Rank
Blogger
Re: LAMP SOCKETS, etal....
Jon Titus   4/10/2012 4:43:01 PM
NO RATINGS
I looked for some brass sockets with brass rivets with the idea that a bit of solder would provide a safer circuit. No such sockets exist, at least on the sites I reviewed. 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...

William K.
User Rank
Platinum
Lamp socket construction sparks danger.
William K.   4/10/2012 5:25:18 PM
NO RATINGS
First a comment about aluminum wiring: it is not a potential problem, it is a real problem. It fails. good jobs last longer than poor jobs before they fail, but they still fail if they are used. Unused aluminum wiring is less of a problem.

If the brass-type alloy in Jon's lamp had been the slightly springy mix, and iff it had been correctly swedged, that would not have been the part that failed. Of course the problem with the 3-way sockets is that only the center contact has any spring, and so the other contact is challenged to stay connected. It was a poor design before it ever left the drawing board. Of course the Edison screw base is a challenge, but when they are made to the original standard they work quite well, and very few people cross-thread them. The main advantage, aside from the huge installed base, is that they don't depend on material springiness to hold the bulb in place. Most alternative bases demand much closer tolerances or much better materials in order to keep the contact presure high enough. And the wonderful sockets in your car would probably not pass the shock hazard and stupid user tests, or else they would be too expensive to compete.

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