Intermittent Light Bulb Failure - Page 1
Forum section: electronics / beginners

author: edy
author_rank: Super Contributor
timestamp: March 23, 2016, 03:25:08 am
content: I have this strange problem, it's driving me nuts! In my kitchen ceiling I have 2 lights... each is a simple socket for a light bulb and then it gets covered by a frosty white globe. The lights are up around 10 foot high and I need to get a ladder and remove the globe each time I need to change the bulb.So I have this one light that is doing a strange thing. It was working fine for months, then a few days ago it flickered a bit and went out. I climbed up the ladder, took off the globe surrounding it, and unscrewed the bulb (which is clear). The light switch was still on. As I turned it I saw some sparks and the light went back on, so I screwed it back in and it worked again for a few days.Then this morning the light was again not turning on. I climbed up the ladder again, removed the globe, unscrewed the bulb completely this time and looked at the filament which was intact. Nothing visibly wrong with it, no sounds when I shook the bulb. I screwed it back into the socket and turned on the light switch... again I had light. Put the globe back over the bulb, ladder back into garage.I figured all was good..... except...... a few hours later it does the same thing! I was upstairs, my wife said it flickered a few times and went out. I try turning on the light again and it's dead again!Now I'm not about to climb up that ladder again until I have an explanation of what is going on! It makes no sense. Is the filament broken? When it heats up after a while does it break a contact somewhere? Then why wouldn't it light up again after the filament got cold? I have to physically unscrew and rescrew the bulb in by only a tiny amount. Could it be carbonation on the contact in the socket? Why would this happen to this socket only and is moving the bulb "scratching" the carbon deposit away until it builds up again?I can't figure this simple thing out... Someone help!

author: IanB
author_rank: Super Contributor
timestamp: March 23, 2016, 03:36:04 am
content: Replace the bulb with a new one...

author: Xenon Photon
author_rank: Unknown
timestamp: March 23, 2016, 03:44:32 am
content: broken bond wires to the screw? or bad connection to the socket wires?!change the bulb and let us know.

author: Brumby
author_rank: Unknown
timestamp: March 23, 2016, 03:56:47 am
content: My experiences with this phenomenon are based on the filament being broken. You might also be having the same problem, but with the break not being visible (remember, electrical connection is what matters - not visual) - but there is the possibility you may be experiencing something similar in the connections in the base which is behaving somewhat the same.....With the visible filament break, the globe can be brought back to life by having the globe powered and manipulating the filament until it makes contact with the other side. A quick surge of current forms a weld - albeit a weak one - which will allow the globe to function for a while. Turning it off will allow things to cool down and it may cause the weld to break, leaving you with a dead globe again. It may be possible to repeat this process, but the law of diminishing returns jumps in real quick.Answer: Replace the globe. If the problem still persists, get an electrician to check the socket.PS. I used the above 'repair' technique in my first job as a computer operator (many moons ago). The IBM 2501 card reader we had used an incandescent light globe to shine through the punch cards to photodetectors underneath. One night, it failed before I had loaded up the night's work. So I popped the top, saw how easy it was to access - and then 'fixed' it (as above). I immediately loaded every single job that was scheduled for that night onto the input queue, crossing my fingers that it would last that long. Which it did.

author: Xenon Photon
author_rank: Unknown
timestamp: March 23, 2016, 04:05:18 am
content: Quote from: Brumby on March 23, 2016, 03:56:47 amYou reminded me of this video:

author: MarvinTheMartian
author_rank: Frequent Contributor
timestamp: March 23, 2016, 04:49:56 am
content: Quote from: Xenon Photon on March 23, 2016, 04:05:18 amLove this guy!

author: SL4P
author_rank: Super Contributor
timestamp: March 23, 2016, 05:15:38 am
content: Without reading all the intelligent replies--- was it an intermittent light bulb, or an intermittent failure?

author: edy
author_rank: Super Contributor
timestamp: March 23, 2016, 05:53:17 am
content: Ok, I just climbed up ladder again and unscrewed the bulb, then screwed it back in. Turn on the light switch and it works again!Intermittent failure... Bulb constant. Only thing required to "fix" is turning it 15 degrees counter-clockwise, then screwing it back 15 degrees clockwise. Bulb is tight in socket, nothing obvious going on with the bulb otherwise. However, I do notice the metal of the bulb screw is silvery white, not copper. It kind of looks like aluminum.... Not sure if that is now being used for bulbs or not. I remember them being a shiny silver and usually copper.

author: MarvinTheMartian
author_rank: Frequent Contributor
timestamp: March 23, 2016, 05:55:59 am
content: Quote from: SL4P on March 23, 2016, 05:15:38 amI'll go with theintermittent light bulb- sometimes it was there, sometimes it was not - a very unusual symptom!

author: Shock
author_rank: Super Contributor
timestamp: March 23, 2016, 06:37:32 am
content: Low wattage halogen light bulb on a dimmer circuit? If so they seem to get blinky depending on what dimmer circuit is being used.If not what type of bulb what voltage and type of circuit?

author: edy
author_rank: Super Contributor
timestamp: March 23, 2016, 06:44:31 am
content: This is a normal incandescent bulb. Clear glass. Probably 60 or 75 W, nothing more. Single filament inside. The thread on the bulb is also standard, with one round contact on the bottom end of the base and the other contact being the threading around the side of the base. The light switch is just a regular 2-pole switch. One on, one off. No dimming. Switch is fine, I hear no crackling and it is smooth.I did notice that the round contact at the end of the base was quite flat. It didn't stick out much. Nevertheless, it still makes contact perfectly fine with the socket when I screw it in. The socket looks to be surrounded in ceramic, not plastic. The bulb metal is aluminum which having done a Google search appears to be fine.

author: Muttley Snickers
author_rank: Unknown
timestamp: March 23, 2016, 06:55:39 am
content: I have in the past encountered the intermittent problem you describe particularly with outdoor Par-38 Edison screw-in type fixtures, generally it's the centre contacts that need a slight rub with emery paper and also the centre contact in the fitting may require being brought forward slightly with a pair of pointy nose pliers, just make sure that power is completely disconnected beforehand.Also just for the record how many people were present during the replacement process and what were their occupations ?......

author: wraper
author_rank: Unknown
timestamp: March 23, 2016, 07:08:35 am
content: Quote from: blueskull on March 23, 2016, 04:02:19 amThis is used for completely different reason though. To burn the conductive debris that got between the electrodes of the CRT.

author: Connoiseur
author_rank: Regular Contributor
timestamp: March 23, 2016, 08:18:02 am
content: I guess the problem is oxidised contacts. Did you try light sanding with 200 -ish grit paper?If none of the remedies work, then probably the bulb is possessed. You might wanna replace or exorcise; whichever is cheaper.

author: Shock
author_rank: Super Contributor
timestamp: March 23, 2016, 08:44:38 am
content: How many electronics engineers does it take for the OP to change a light bulb?

author: Delta
author_rank: Super Contributor
timestamp: March 23, 2016, 11:12:28 am
content: Just change the bloody bulb!

author: dB
author_rank: Newbie
timestamp: March 23, 2016, 12:04:08 pm
content: Quote from: edy on March 23, 2016, 03:25:08 amYou said you had 2 lights/sockets? Switch the bulbs between sockets. That will tell you if it's the bulb or the socket!!!

author: tooki
author_rank: Super Contributor
timestamp: March 23, 2016, 01:42:27 pm
content: Quote from: edy on March 23, 2016, 05:53:17 amAre youabsolutely positivethe bulb is to blame? I ask because I had the same symptoms, and it turned out the bulb was just fine, it was the light switch that was intermittent. Next time it flickers, try switching the light switch off and on a few times. If it stabilizes, it's probably the switch. If not, then it's the bulb or the socket.

author: cvanc
author_rank: Frequent Contributor
timestamp: March 23, 2016, 01:50:28 pm
content: Quote from: Muttley Snickers on March 23, 2016, 06:55:39 amThis. Your center contact in the socket (a flat metal tab) needs to mate better with the center contact of the bulb (which you said was kind of flat). A common problem (at least in my house).Fashion a tool to pull the center tab out to a more raised position and/or put a small bump of solder on the center contact of the bulb.

author: JoeO
author_rank: Frequent Contributor
timestamp: March 23, 2016, 02:10:46 pm
content: Call an electrician. This is a problem that is way to difficult to troubleshoot over the internet.

author: Audioguru
author_rank: Super Contributor
timestamp: March 23, 2016, 02:29:24 pm
content: I suspect that the light bulb socket has poor contact caused by corrosion maybe from a leak up there or from water vapour rising into the light bulb globe caused by cooking and dishwashing in the kitchen.Hey! This is 2016. Old fashioned filament light bulbs are illegal and are not available today aren't they? I have been using efficient compact fluorescent light bulbs for the last 12 years or more.

author: Cubdriver
author_rank: Unknown
timestamp: March 23, 2016, 04:12:35 pm
content: Two light fixtures. Two bulbs. Swap bulbs between sockets. If problem follows bulb, replace intermittent bulb. If problem stays with the same socket, troubleshoot socket and wiring thereto.-Pat

author: Audioguru
author_rank: Super Contributor
timestamp: March 23, 2016, 06:56:20 pm
content: I had a home that was wired with huge aluminum wires that fit poorly on receptacles and light sockets. The connections were intermittent all over the place and they even smoked sometimes. I replaced all the receptacles with aluminum-safe ones.I wonder if electrical receptacles are intermittent when they have the "stick the stripped wire in the hole and hope it makes a good contact"?

author: Psi
author_rank: Super Contributor
timestamp: March 23, 2016, 07:57:21 pm
content: When there's a bad connection the contacts heat up and it stuffs the contact spring. Further arcing eats away at the contact plating. You end up with a week spring pushing dirty contacts and get an intermittent connection.So my guess is a bad socket

author: edy
author_rank: Super Contributor
timestamp: March 23, 2016, 09:53:21 pm
content: Quote from: Audioguru on March 23, 2016, 02:29:24 pmYes, and I had a CFL in this exact same socket and it only lasted less than 2 years! I blamed it on the fact that it was inside a "globe" enclosure which poorly restricted ventilation and the bulb was oriented "upside down" with all the electronics pointing up into the socket and the CFL below perhaps causing the heat to rise up and fry it.I even have a teardown of it and tried to figure out what went wrong here.... hence the reason why I went back to a regular tungsten filament bulb:Ok, so I will try to swap bulbs, and check the spring inside the middle of the socket. The damn thing is mounted really high up in the ceiling and almost directly above a heavy table so it is a real pain getting up there. I am convinced the bulb is fine. It must be an issue with the way it is making contact in the socket. I'll take some photos soon to show you!

author: edy
author_rank: Super Contributor
timestamp: March 24, 2016, 01:10:19 pm
content: I have attached photos of the possessed light bulb.

author: Delta
author_rank: Super Contributor
timestamp: March 24, 2016, 02:41:29 pm
content: JUST CHANGE THE BLOODY BULB! Please!

author: edy
author_rank: Super Contributor
timestamp: March 24, 2016, 02:42:53 pm
content: Quote from: Delta on March 24, 2016, 02:41:29 pmWait the story gets better...

author: CatalinaWOW
author_rank: Super Contributor
timestamp: March 24, 2016, 03:05:58 pm
content: Quote from: Psi on March 23, 2016, 07:57:21 pmRing a ding ding. This has been the cause I have found most often in this situation. While a bulb can weld itself back together I have seldom had one do that more than once or twice. Occasionally I have found loose screws at the wire attachment. So a socket replacement is in your future. Too bad it is not easily accessible.

author: edy
author_rank: Super Contributor
timestamp: March 24, 2016, 04:56:06 pm
content: I pulled on the center contact and tried the bulb again. This time it also worked a few seconds but then turned off. As I tried to wiggle the bulb tight and loose, I heard a "grinding" noise and understood it meant the glass was tearing from the aluminum threading and my bulb was getting destroyed. I carefully unscrewed the bulb to avoid damaging it further and having half of it stuck inside the socket.Here are the photos.... So definitely it's no longer an option to use this otherwise perfectly good bulb.The way it was constructed, the center pin of the bulb goes up that thin wire up through one side of the glass tube.... but the pin just gets soldered or perhaps spot-welded to the side top of the thread. That brown looking gunk appears to be whatever adhesive they used to join the glass part of the bulb to the aluminum base. But it looks burnt and powdery.It is all deteriorated and I'm not sure if this was causing the fault. It would not have been able to cause a short otherwise I would have seen sparks and smoke and the fuse would have tripped. It was not a thermal issue either because even a hot bulb, once unscrewed and rescrewed would work.... or was it?

author: edy
author_rank: Super Contributor
timestamp: March 24, 2016, 05:06:51 pm
content: This might be the clincher that explains it.... What is the photo showing...Should have had my glasses on... and brain on.

author: edy
author_rank: Super Contributor
timestamp: March 25, 2016, 01:42:26 am
content: The solution.For those of you who are just joining in, or didn't realize it, the bulb I was using was 100 W and the socket 60 W max. It likely overheated and ruined the bulb bonding wires or caused some film deposit on the contacts. For whatever reason, rather than the socket wires melting and fusing together (causing a short), the failure resulted in the bulb going OUT, which may have helped prevent a fire. However, the bulb was not visibly damaged (filament intact) and would work again once re-inserted, which was puzzling. A few twists of the bulb and each time it would work again for a few more days before going out. Finally I realized what the problem was and bought a 100 W CFL that actually only uses 23 W, giving me the lumens I want but keeping well within the heat tolerance of the fixture.I declare this thread CLOSED. Hopefully my stupidity will help someone else avoid the same mistake.

author: RobertoLG
author_rank: Frequent Contributor
timestamp: March 25, 2016, 02:45:38 am
content: why didn't you get some led ones, 10 W are pretty good

author: Audioguru
author_rank: Super Contributor
timestamp: March 25, 2016, 02:57:08 am
content: The photo of the light bulb shows that the wire that is supposed to be welded on the metal screw part is not welded where it is supposed to be.Was the "no name brand" light bulb also made in China?Aren't permanent electrical products supposed to be certified?

author: edy
author_rank: Super Contributor
timestamp: March 25, 2016, 03:31:09 am
content: Quote from: Audioguru on March 25, 2016, 02:57:08 amYou are correct, it probably wasn't welded well and perhaps as the fixture heated up it expanded just enough to break the contact. It was likely made in China... I noticed that area was a bit charred a few times when I took out the bulb to inspect it. When I screwed it in again, I may have "sandwiched" the bond wire to the metal screw part just a bit more without realizing it. Then as the bulb ran the heat must have distorted things just enough that eventually the wire would shift a small amount, arc across the gap, form a burn layer and then no longer conduct until I rubbed the parts together again accidently as I screwed and unscrewed the bulb.Quote from: RobertoLG on March 25, 2016, 02:45:38 amI found some LED bulbs but they were over-priced at the store and these CFL's seemed like a better deal. I know in the long run we'll all need to move over to LED but I hope as we do the prices will drop.

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2016, 06:06:32 am
content: It is actually meant to be soldered, just they did not actually solder it, the 8 year old child doing it must have skipped doing that one, or it was knock off time. Incidentally this is the one application where they use a high lead solder, as a tin solder will grow whiskers from the heat. Bit hard though to solder to aluminium though, you can see the dab of sulphuric acid used to etch the surface still is there.As to what is joining the glass to the base, that is actually cement, like you use to build walls, blended with fine sand and a surfactant so it will have entrained air in it to increase volume. Nothing else sticks to glass and withstands running at 600C for decades, though most of the actual holding is in the mechanical filling of the shape, not the weak bond to the glass, it is all mechanical bonding to the rough surfaces in the glass join.

author: WackyGerman
author_rank: Regular Contributor
timestamp: March 25, 2016, 10:23:29 am
content: Just bend the contacts from the socket closer to the builb that the contacts touches properly

author: Delta
author_rank: Super Contributor
timestamp: March 25, 2016, 04:27:17 pm
content: Well motherfuck me, after more words than War and Peace, nearly as many posts as the 800% thread, you change the fucking bulb and the lamp stays on! Well what a revelation!Q) How many posts to an engineering forum does it take to change a light bulb?A) Far too bloody many!

author: SeanB
author_rank: Super Contributor
timestamp: March 25, 2016, 05:11:26 pm
content: Quote from: Delta on March 25, 2016, 04:27:17 pmYou should read the real book, not the Readers Digest Condensed version..............Now, on to something more serious, how many EE's does it take to move a socket outlet?

author: Cubdriver
author_rank: Unknown
timestamp: March 25, 2016, 05:17:19 pm
content: Quote from: Delta on March 25, 2016, 04:27:17 pmYeah, huh? In the end it was the friggin' light bulb, as I suspected from when I read the first post. Suspect the most likely failure point - the incandescent lamp in this case...-Pat