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Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
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#1
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LED Light Emitters: Failure Mode?
Do LED lights fail completely or gradually?
i.e are they all-or-nothing? I've got a nice little LED flashlight that, one day, started getting dim. Noticed that some of the contacts were corroded and wire-brushed the ones on the back of the emitter module. The plate that connects the two stacks of AA batteries in the back recess of the light's body is inaccessible so, after scratching it a little with a long knife to no avail, I folded up some alu foil and stuffed it down there... but still no luck. Fooled around with it today, and couldn't even get a dim light by applying 6v from a known good source to the feet of the emitter module. My first thought was that I'd hosed the LED completely by accidentally applying reverse polarity somewhere along the line. Possible? If not, what about the gradual dimming? Does that fit with LED failure, or does it narrow the cause down to some sort of electrical contact issue? -- PeteCresswell |
#2
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LED Light Emitters: Failure Mode?
Meat Plow wrote:
On Sat, 19 Jan 2008 10:52:36 -0500, (PeteCresswell) wrote: Do LED lights fail completely or gradually? i.e are they all-or-nothing? I've got a nice little LED flashlight that, one day, started getting dim. Noticed that some of the contacts were corroded and wire-brushed the ones on the back of the emitter module. The plate that connects the two stacks of AA batteries in the back recess of the light's body is inaccessible so, after scratching it a little with a long knife to no avail, I folded up some alu foil and stuffed it down there... but still no luck. Fooled around with it today, and couldn't even get a dim light by applying 6v from a known good source to the feet of the emitter module. My first thought was that I'd hosed the LED completely by accidentally applying reverse polarity somewhere along the line. Possible? If not, what about the gradual dimming? Does that fit with LED failure, or does it narrow the cause down to some sort of electrical contact issue? An LED can grow dim if the input voltage is too high but I've never heard of one gradually dimming. This does not mean that it doesn't happen of course. I have several of those little led keyring torches, and they do grow dimmer after a time compared with new ones even with brand new batteries. Ron(UK) |
#3
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LED Light Emitters: Failure Mode?
Gradual dimming is the normal way LEDs wear out. I thought it took years,
though. |
#4
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LED Light Emitters: Failure Mode?
"Meat Wanka" wrote in message ... On Sat, 19 Jan 2008 17:07:49 +0000, Ron(UK) wrote: Meat Plow wrote: On Sat, 19 Jan 2008 10:52:36 -0500, (PeteCresswell) wrote: Do LED lights fail completely or gradually? i.e are they all-or-nothing? I've got a nice little LED flashlight that, one day, started getting dim. Noticed that some of the contacts were corroded and wire-brushed the ones on the back of the emitter module. The plate that connects the two stacks of AA batteries in the back recess of the light's body is inaccessible so, after scratching it a little with a long knife to no avail, I folded up some alu foil and stuffed it down there... but still no luck. Fooled around with it today, and couldn't even get a dim light by applying 6v from a known good source to the feet of the emitter module. My first thought was that I'd hosed the LED completely by accidentally applying reverse polarity somewhere along the line. Possible? If not, what about the gradual dimming? Does that fit with LED failure, or does it narrow the cause down to some sort of electrical contact issue? An LED can grow dim if the input voltage is too high but I've never heard of one gradually dimming. This does not mean that it doesn't happen of course. I have several of those little led keyring torches, and they do grow dimmer after a time compared with new ones even with brand new batteries. Cheap *******s, how dare they! OK, Meat Wanka - we're in your parlour now. Let's see what Mr Big Mouth Show-Off's like when he's at home.... (I'll be in touch soon, sweedie.... ;-) |
#5
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LED Light Emitters: Failure Mode?
"mc" wrote in message ... Gradual dimming is the normal way LEDs wear out. I thought it took years, though. If you overdrive them it will happen much faster. I've done that a few times playing with LEDs. Mike |
#6
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LED Light Emitters: Failure Mode?
"(PeteCresswell)" wrote in message ... Do LED lights fail completely or gradually? i.e are they all-or-nothing? I've got a nice little LED flashlight that, one day, started getting dim. Noticed that some of the contacts were corroded and wire-brushed the ones on the back of the emitter module. The plate that connects the two stacks of AA batteries in the back recess of the light's body is inaccessible so, after scratching it a little with a long knife to no avail, I folded up some alu foil and stuffed it down there... but still no luck. Fooled around with it today, and couldn't even get a dim light by applying 6v from a known good source to the feet of the emitter module. My first thought was that I'd hosed the LED completely by accidentally applying reverse polarity somewhere along the line. Possible? If not, what about the gradual dimming? Does that fit with LED failure, or does it narrow the cause down to some sort of electrical contact issue? **White LEDs wear out pretty quickly. They are a blue LED with a fluorescent coating. The coating fails. Regular coloured LEDs can last for many decades, whilst I've found white LEDs will dim to around 30% of their original output after about 1 - 2 years of continuous duty (at rated current). Higher currents will accelerate that wear. Trevor Wilson |
#7
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LED Light Emitters: Failure Mode?
On Sat, 19 Jan 2008 16:51:16 -0500, "Michael Kennedy"
wrote: "mc" wrote in message .. . Gradual dimming is the normal way LEDs wear out. I thought it took years, though. If you overdrive them it will happen much faster. I've done that a few times playing with LEDs. Mike I have some blue Philips LED christmas lights that I was using as a night light. After they were on 24/7 for a year a number of LEDs had failed short circuit and the rest were 50-75% dimmer than new. I was very disappointed with them. Ordinary light bulbs last longer than that! They were either using cheap LEDs, or over driving them (or both). Looking directly into the dim LEDs I could see large dark areas on the dice. Andy Cuffe |
#8
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LED Light Emitters: Failure Mode?
"Trevor Wilson" wrote in message ... "(PeteCresswell)" wrote in message ... Do LED lights fail completely or gradually? i.e are they all-or-nothing? I've got a nice little LED flashlight that, one day, started getting dim. Noticed that some of the contacts were corroded and wire-brushed the ones on the back of the emitter module. The plate that connects the two stacks of AA batteries in the back recess of the light's body is inaccessible so, after scratching it a little with a long knife to no avail, I folded up some alu foil and stuffed it down there... but still no luck. Fooled around with it today, and couldn't even get a dim light by applying 6v from a known good source to the feet of the emitter module. My first thought was that I'd hosed the LED completely by accidentally applying reverse polarity somewhere along the line. Possible? If not, what about the gradual dimming? Does that fit with LED failure, or does it narrow the cause down to some sort of electrical contact issue? **White LEDs wear out pretty quickly. They are a blue LED with a fluorescent coating. The coating fails. Regular coloured LEDs can last for many decades, whilst I've found white LEDs will dim to around 30% of their original output after about 1 - 2 years of continuous duty (at rated current). Higher currents will accelerate that wear. Trevor Wilson I believe that some of these LED flashlights use drive electronics built into the head, to pulse the LEDs rather than DC drive them. It apparently produces a greater light density per amp, and helps to prolongue the life of the LEDs. It's possible that the one that has failed may have such electronics, and that's where the problem lies ?? Arfa |
#9
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LED Light Emitters: Failure Mode?
"Andy Cuffe" wrote in message
... I have some blue Philips LED christmas lights I was using as a night light. After they were on 24/7 for a year, a number of LEDs had failed short-circuit, and the rest were 50-75% dimmer than new. I was very disappointed -- ordinary light bulbs last longer than that! They were either using cheap LEDs, or overdriving them (or both). Looking directly into the dim LEDs I could see large dark areas on the dice. Don't do that! You'll put your eye out! |
#10
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LED Light Emitters: Failure Mode?
On Sun, 20 Jan 2008 06:46:09 -0800, William Sommerwerck wrote:
"Andy Cuffe" wrote in message ... I have some blue Philips LED christmas lights I was using as a night light. After they were on 24/7 for a year, a number of LEDs had failed short-circuit, and the rest were 50-75% dimmer than new. I was very disappointed -- ordinary light bulbs last longer than that! They were either using cheap LEDs, or overdriving them (or both). Looking directly into the dim LEDs I could see large dark areas on the dice. Don't do that! You'll put your eye out! Maybe _that_ explains the "large dark areas ...." |
#11
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LED Light Emitters: Failure Mode?
"Arfa Daily" wrote in message ... "Trevor Wilson" wrote in message ... "(PeteCresswell)" wrote in message ... Do LED lights fail completely or gradually? i.e are they all-or-nothing? I've got a nice little LED flashlight that, one day, started getting dim. Noticed that some of the contacts were corroded and wire-brushed the ones on the back of the emitter module. The plate that connects the two stacks of AA batteries in the back recess of the light's body is inaccessible so, after scratching it a little with a long knife to no avail, I folded up some alu foil and stuffed it down there... but still no luck. Fooled around with it today, and couldn't even get a dim light by applying 6v from a known good source to the feet of the emitter module. My first thought was that I'd hosed the LED completely by accidentally applying reverse polarity somewhere along the line. Possible? If not, what about the gradual dimming? Does that fit with LED failure, or does it narrow the cause down to some sort of electrical contact issue? **White LEDs wear out pretty quickly. They are a blue LED with a fluorescent coating. The coating fails. Regular coloured LEDs can last for many decades, whilst I've found white LEDs will dim to around 30% of their original output after about 1 - 2 years of continuous duty (at rated current). Higher currents will accelerate that wear. Trevor Wilson I believe that some of these LED flashlights use drive electronics built into the head, to pulse the LEDs rather than DC drive them. It apparently produces a greater light density per amp, and helps to prolongue the life of the LEDs. It's possible that the one that has failed may have such electronics, and that's where the problem lies ?? **Certainly possible. However, it depends on the electronics driving the LED. Manufacturers have a tendency to drive the LED as hard as possible, in order to obtain maximum brightness. They don't care if the thing fails in six months. The money is already in the bank. Trevor Wilson |
#12
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LED Light Emitters: Failure Mode?
"Meat Wanka" wrote in message ... On Sat, 19 Jan 2008 21:43:50 +0000, Keith G wrote: OK, Meat Wanka - we're in your parlour now. Let's see what Mr Big Mouth Show-Off's like when he's at home.... (I'll be in touch soon, sweedie.... ;-) Yawn------- Aww..... Meat Wanka's tired - must be past his bedtime! (Perhaps he should try wearing boxing gloves at night - then he'd not be so *beat up* during the day! :-) At least his tits aren't still slapping the keyboard.... |
#13
Posted to sci.electronics.repair
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LED Light Emitters: Failure Mode?
"(PeteCresswell)" wrote in message ... Do LED lights fail completely or gradually? i.e are they all-or-nothing? I've got a nice little LED flashlight that, one day, started getting dim. Noticed that some of the contacts were corroded and wire-brushed the ones on the back of the emitter module. The plate that connects the two stacks of AA batteries in the back recess of the light's body is inaccessible so, after scratching it a little with a long knife to no avail, I folded up some alu foil and stuffed it down there... but still no luck. Fooled around with it today, and couldn't even get a dim light by applying 6v from a known good source to the feet of the emitter module. My first thought was that I'd hosed the LED completely by accidentally applying reverse polarity somewhere along the line. Possible? If not, what about the gradual dimming? Does that fit with LED failure, or does it narrow the cause down to some sort of electrical contact issue? -- PeteCresswell It depends on the LED, some of them do in fact grow dim, the blue LEDs on my PC used to be identical, now the hard drive LED is considerably brighter than the power LED which is on far more. The phosphor coated LEDs dim even faster, white and pink LEDs are a phosphor over a blue chip. I've had some too that got dim and flickered. I don't know the exact mechanism of failure. |
#14
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LED Light Emitters: Failure Mode?
I have some blue Philips LED christmas lights that I was using as a night light. After they were on 24/7 for a year a number of LEDs had failed short circuit and the rest were 50-75% dimmer than new. I was very disappointed with them. Ordinary light bulbs last longer than that! They were either using cheap LEDs, or over driving them (or both). Looking directly into the dim LEDs I could see large dark areas on the dice. Andy Cuffe I have some too that have bad LEDs, they flickered horribly as well, one set I modified with a rectifier and it was MUCH nicer looking then, it lasted a couple years but now has one dim flickering LED. My friend gave me some more sets which had not been modified and they have several more bad LEDs so it isn't the rectifier that did it. I'm not impressed with LED Christmas lights, they're just not there yet. |
#15
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LED Light Emitters: Failure Mode?
"James Sweet" wrote in message
news:6kWkj.4026$Ev6.189@trndny07... I have some too that have bad LEDs, they flickered horribly as well, one set I modified with a rectifier and it was MUCH nicer looking then, it lasted a couple years but now has one dim flickering LED. My friend gave me some more sets which had not been modified and they have several more bad LEDs so it isn't the rectifier that did it. I'm not impressed with LED Christmas lights, they're just not there yet. What you're saying suggests that the LEDs are simply connected across the power line in series, with the LEDs serving as their own rectifiers, so to speak. Glitches and spikes in the "reverse" direction aren't going to do the LEDs any good. Adding a rectifier presumably provides protection. |
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