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These lampholders are designed to disconnect power to the lamp contacts when the lamp is removed. It's to prevent kids getting a shock from an open lamp holder. Thankfully eBay, wish and amazon have addressed this by supplying lamps with live connections all over the outside.
This one had failed in manner that caused random arcing and flickering of the lamp. I thought it would be interesting to see what had failed, and the general internal construction of the holder.
It's worth noting that modern lamps pose much less thermal stress on traditional lamp holders. But it wouldn't surprise me if they start making cost-optimised "LED-only" lamp holders.
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Is quite an interesting thing i'm in crew accommodation at the moment. And when when we moved in there was one of the lights kept flickering in the hallway. I fixed it by replacing the lamp holder because this existing lamp holder was arcing internally. And it's quite unusual because it's a safety lamp holder and i never actually seen one of these in the flesh.

So far so well what better thing to do than take it. Apart. Let's get down closer to this so. Here's the idea in the uk.

We have what are called bainit cap lamp holders. Which are the two pins out the side and then the two contacts the end and this is not electrically connected to anything some sometimes it's grounded. But usually it's just live neutral. Whichever priority you put it in with the normal socket.

You've got the two pins at the back. And if you were to poke your finger into it you could get an electric shock. However with this socket when you put it in it hits an interlock and it the pins aren't live until you actually twist the lamp. But this is making crunching noises.

This is not twisting. I think that may be the problem the back of it has already suffered plastic fatigue and has snapped off let's get a screwdriver and pry this apart and see how it comes apart. I can see little tangs here. Oh.

That's not so bad. This is very brittle. I think this lamp holder is old enough to belong to the era of uh tungsten lamps that are very hot okay right there's where it was arcing so the connections in the back uh just come down to these two pins that then rub onto these contacts and i'm going to guess. I'm going to guess that when i put this in and rotate.

Oh. It's scrunching. It's yeah. I don't think that was supposed to happen uh.

Let's just keep exploring it then oh. This is absolutely baked let's keep going down. I shall poke the guts out oh this is crumbly to bits. It's just absolutely wrecked.

Where is the other spring. Oh there's other spring. I think now it's actually stayed in place. Oh.

The plastic's broken that's why around there so how does this mechanism here is the shutter that rotates is it just rotating well now i've removed the crunchy bits let me see if i can reassemble this so. When the lamps put in when the lamp's put in it is rotating that plate inside okay um and when it rotates that plate inside. I'm guessing that these contacts that come down onto these pins probably have little uh. They do have little spring loaded contacts underneath not quite sure they were supposed to go in oh.

They're supposed to go in like that and that in rotating um all right. I'm just gonna have to have another go at this so the actual the contact pins stay put. But this rotates and i'm guessing then that this springy contact does just rotate onto these pins. It must move and slide on them all right tell you what i'm going to try and assemble this it could take a while to work out this puzzle.

But i shall try and assemble it and see if i can work out what's going on here one moment. Please well that didn't take too long. I've worked out how it works as you twist the lamp. It actually slides those contacts backwards and forwards.

I thought they were going to rotate. But they actually slide sideways. So these are sliding contacts on the top here and it just sits in these tangs and when they slide. They move backwards and forwards this spring loaded contact and to make contact with uh.

The actual pin in the back of the actual socket. The one that the lamp is making connection to so that's interesting an interesting mechanism different different different to what i was expecting this one is definitely showing the signs of heat. There's a certain thing that you know led lamps may kind of bake themselves. I mean we've featured this many times this channel.

But uh technically speaking. Now the lamp holders are going to last a lot longer because they're not subject to the same thermal fatigue. They used to be so uh very interesting actually i'm glad that failed now and so we could take it apart and see how it worked that was quite fun.

13 thoughts on “Inside a failed safety lamp holder.”
  1. Avataaar/Circle Created with python_avatars criggie says:

    I'm digging "Big Clive On Tour" you want to do a portable bare-minimum travel kit. One of those cutting mats, lights/camera/stand/laptop, spudger, screwdrivers, what else would you need?
    Probably not the sodastream, might make flights awkward.

  2. Avataaar/Circle Created with python_avatars Tsunauticus IV says:

    You might have prevented a fire. A fire that cost money… and possibly lives. You’re a true hero Clive. Little things like that are what separate good humans from bad. You care about the safety of property and people. Bravo brother. 👏

  3. Avataaar/Circle Created with python_avatars Jason Halverson says:

    surprising how much safer your plugs and outlets are over there. granted you also have twice the voltage, but still. you'd think they could still come up with something safer here too

  4. Avataaar/Circle Created with python_avatars PyroRob69 says:

    The sliding contacts seem to be a way to keep them clean, or less corroded.

  5. Avataaar/Circle Created with python_avatars RV Sparky says:

    Whom would u love to have stay at urplace. Bigclive or Electroboom ?

  6. Avataaar/Circle Created with python_avatars Ian Gardener says:

    'Keep going down', you sound like my ex wife.

  7. Avataaar/Circle Created with python_avatars Jimmy B says:

    I mean, you could just turn off the power before changing the bulb. Or just not put your fingers in spicy holes.
    Amazing the enginerding being spent on preventing people from receiving well deserved Darwin awards.

  8. Avataaar/Circle Created with python_avatars Paul McCoy says:

    There is (was?) a similar but uncommon style of safety lamp holder in the U.S. for the Edison screw-type bulbs. The screw section is made in two pieces with the upper (lower? forward, maybe?) portion being stationary and the lower portion being drawn towards the upper by the screw threads. Power is only applied to the center pin once the bulb has been screwed in far enough to draw the contact into it from behind. The problem is that it only works with bulbs with properly-made screw threads, not the cheap junk that’s usually available.

  9. Avataaar/Circle Created with python_avatars d. t. says:

    Cool. Crunchy electrical fittings! Someone should patent that. Good luck. 👍

  10. Avataaar/Circle Created with python_avatars Lu Woods says:

    Hope you engaged a safety squint at some point.

  11. Avataaar/Circle Created with python_avatars Fred Bloggs says:

    Looks to me (without having one to examine) that the connection is made by the moving of the pins when the bulb is pushed in. The sliding bit is just to facilitate locking the bulb in. Then again, as I said, without one to examine I may be completely wrong.

  12. Avataaar/Circle Created with python_avatars Plasmaburndeath says:

    Such a twisted video Clive, keep them up 🙂

  13. Avataaar/Circle Created with python_avatars mozismobile says:

    mmm, saftey lamp with burnt crunch bits… so tasty!

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