Teardown of el-cheapo fluorescent energy-saving lamp - Page 1
Forum section: electronics / general

author: wkb
author_rank: Super Contributor
timestamp: January 22, 2012, 05:43:06 pm
content: One of my fluorescent "energy saving" lamps just died on me, which obviously gave me an excuse to dismantle it to inspect it's guts.As you can see, really high-quality soldering, but oh-so-RoHS compliantA money saver it for sure was not, typical case of infant mortality.

author: SeanB
author_rank: Super Contributor
timestamp: January 22, 2012, 05:54:12 pm
content: So what died? Bridge diodes, transistor and of course the fusible resistor. Capacitor may have gone open circuit as well.

author: wkb
author_rank: Super Contributor
timestamp: January 22, 2012, 06:00:05 pm
content: Quote from: SeanB on January 22, 2012, 05:54:12 pmI have not tried to troubleshoot it. I did notice some rather lousy soldering on both one through-hole component as well as a multiple SMD components.

author: SeanB
author_rank: Super Contributor
timestamp: January 22, 2012, 06:26:54 pm
content: What do you expect from a product made by the cheapest supplier using the cheapest parts, assembled by the lowest cost poorly trained labour using the cheapest equipment. Amazing that most work when you buy them, as I often have faulty ones in a big batch, so I prefer to pay more for the better quality ones.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 22, 2012, 07:04:46 pm
content: Quote from: SeanB on January 22, 2012, 06:26:54 pmwhat is better quality brand? i have bunch of philips flou's that died, almost the same circuit as posted above. now i have in stock many type of brand, each time i replace, i will write the date on it, so i can check which one will last longer than others. your recommendation may speed this process up dramatically.

author: Neilm
author_rank: Super Contributor
timestamp: January 22, 2012, 07:30:06 pm
content: I remember reading an article in a magazine that said that poor quality "energy saving" light bulbs might actually waste more power than ordinary light bulbs. This is because they would produce harmonics on the mains that would cause parts to heat up and waste power.Neil

author: Zero999
author_rank: Super Contributor
timestamp: January 22, 2012, 07:40:07 pm
content: Quote from: Neilm on January 22, 2012, 07:30:06 pmYou mean they have a poor power factor.Any fluorescent lamp under 100W will not have a power factor correction unit which is the case for all CFLs.I doubt they really waste more power than the equivalent incandescent, even when the power factor is taken into account.

author: Neilm
author_rank: Super Contributor
timestamp: January 22, 2012, 07:45:48 pm
content: Quote from: Hero999 on January 22, 2012, 07:40:07 pmNot the power factor, but the switching they used would cause harmonics on the mains, causing parts of the supply chain (transformers and the like) to heat up. Harmonics are covered considered under EMC legislation.Neil

author: IanB
author_rank: Super Contributor
timestamp: January 22, 2012, 07:47:06 pm
content: The real issue with CFLs is the vastly increased complexity of manufacture and consumption of resources (look at all those disposable electronics in every lamp). Even if they get recycled they will be shipped by the container load to China where they will be processed in human misery factories. Then of course there is the mercury content, multiplied by the billion for every lamp made. Sometimes when the lamps fail they overheat and cause fires, leading to further costs.CFLs are born out of politics, not science, and few political decisions are good ones.

author: Neilm
author_rank: Super Contributor
timestamp: January 22, 2012, 07:48:56 pm
content: Quote from: IanB on January 22, 2012, 07:47:06 pmAmen to that - CFLs, Lead free solder, the list goes on.Neil

author: kripton2035
author_rank: Super Contributor
timestamp: January 22, 2012, 08:37:29 pm
content: it's time to switch to led lights ...I'm pretty sure the quality of the led lights supply is not more than this cfl light,but at least it consumes really less power...

author: siliconmix
author_rank: Frequent Contributor
timestamp: January 22, 2012, 08:43:09 pm
content: the bumf on these energy saver bulbs is that they last ten years .my arse.3 to 5 average i've experienced.i'd take them back but i forget where i bought them.great things mind use less juice you just have to put up with falling down the stairs every no and then

author: oliver602
author_rank: Regular Contributor
timestamp: January 22, 2012, 08:48:43 pm
content: Wouldn't it be better to have the electronics in the light fitting instead of attached to the bulb? more room to keep cool etc, less waste. Besides 'lack of adoption'(are there domestic fittings like this available? I can't find any) is there a technical reason for this?

author: westfw
author_rank: Super Contributor
timestamp: January 22, 2012, 08:56:46 pm
content: See alsohttp://www.instructables.com/id/Take-apart-a-Compact-Fluorescent-Bulb/

author: Zero999
author_rank: Super Contributor
timestamp: January 22, 2012, 09:31:10 pm
content: Quote from: Neilm on January 22, 2012, 07:45:48 pmI don't think you understand, the poor power factor and switching noise are separate issues.High frequency noise generated by the switching transistors, doesn't travel very far and doesn't cause any problems in the power supply chain but it can interfere with other pieces of equipment: radio, TV, etc.The poor power factor is a result of the current drawn by the CFL not being in proportional with the mains voltage. The input of a CFL consists of a bridge rectifier with a capacitor connected across it. Current is only drawn from the mains when the voltage is 0.7V greater than the voltage on the capacitor so the resulting current waveform consists of high current peaks every time the mains voltage passes through 90oand 270o.The distorted current waveform causes problems in the electrical supply chain: the high current pulses and associated harmonics cause greatier heating in transformer cores and triple-n harmonics add together in the neutral conductor, resulting in a higher current than predicted.Quote from: oliver602 on January 22, 2012, 08:48:43 pmYou can buy lamp fixtures with built-in drive electronics for CFLs. The problem is, the ballast has to be matched to the tube so you can't put a 7W tube into a fitting designed for a 15W lamp and most CFLs are designed to retrofit fitting designed for incandescents.I suppose it's possible to develop a system to tag each CFL so the ballast knows the power rating and delvers the correct current but it's probably not worth the development cost and standardising it wouldn't be easy.

author: PStevenson
author_rank: Regular Contributor
timestamp: January 22, 2012, 10:23:32 pm
content: these are pretty cool things for salvagers like myself, minus the hardware of course there are enough parts in a CFL to make a really nice treble booster overdrive for guitar.where I live these things actually come in the post from the council for free (I didn't request them they just send them, I don't know why and when I contacted them, they didn't know why either, nor did they stop) so having gained a cupboard full of the things I started dismantling them, I don't use them much since I started using LED lights, definitely worth salvaging from if you're that type.

author: jerry507
author_rank: Regular Contributor
timestamp: January 23, 2012, 07:17:34 am
content: Quote from: PStevenson on January 22, 2012, 10:23:32 pmIn Iowa, the power company sends them to you for free if you ask them. They hate building new power plants because of the cost and risk, so they'd much rather have homes drawing a lot less energy to make room for industry. The US will start phasing out incandescent bulbs in 2014, I gather a few countries like Australia and others have already started. Despite naysayers, this is quite a good thing

author: westfw
author_rank: Super Contributor
timestamp: January 23, 2012, 08:56:05 am
content: CFLs are rather a kludge of a replacement for incandescants, though. A sort of "where's the worst possible place to put an electronic ballast." Sigh. And few fixtures are well-designed for CFLs. And the brightness claims are frequently bogus and usually not enough (I used to have a 200W desk lamp and 300W halogen torchieres. The energy efficient replacement is "remodel the house." (the kitchen is nice. three dual four-foor t12 tube fluoresents in the ceiling, plus small t5 fluorescents under each cabinet, plus occasional halogen spots. All I need is an extra 12 inches between floors, and I could do that everywhere. (but let's not get started on what building codes actually require!)) (actually, the replacement is "use twice as many lamps and put up with it being dimmer.")For CFL, I rather like Ikea for both their bulbs and fixtures, though I usually end up buying the cheap CFLs at the local bulk store. In general, I haven't found name-brands to be significantly better than no-names. Nor cheap lights with external electronic ballasts to be that much more reliable than CFLs (just ... much harder to fix.) The "obvious" failures involve swollen and burst electrolytics, but I don't know for sure whether that was the initial failure or a result of failure somewhere else; there are frequently other failures as well (but: component with finite and exponentially decaying lifetime based on temperature, stuffed inside a lamp base...)It'd be interesting to see a series of projects (for hobbyists) based on CFL guts...

author: wkb
author_rank: Super Contributor
timestamp: January 23, 2012, 09:24:51 am
content: Believe it or not: #2 out of a batch of 3 said 'pop' this morning. Apparantly something in the electronics went south

author: Rerouter
author_rank: Super Contributor
timestamp: January 23, 2012, 10:35:21 am
content: kinda looks like you could get a few bits of a switch mode supply out of it, but the real question on my mind is, if one went and redesigned those boards with ceramic caps, and to be all the more reliable, would it exceed or fall short of the cost of replacing the crappy ones every few months

author: kripton2035
author_rank: Super Contributor
timestamp: January 23, 2012, 12:12:40 pm
content: I still cannot understand why people loose time and money to build, buy and fix these cfl lightsthe led lights are more interesting in many points ...

author: westfw
author_rank: Super Contributor
timestamp: January 23, 2012, 06:05:43 pm
content: I can't get a 75W equivalent LED light for a reasonable price, and that's about the minimum that I need for many fixtures.Also, existing LED lights aren't living up to their promises either; many use inferior quality LEDs whose output degrades quite rapidly, efficiency is similar to CFLs, and the power supplies are frequently subject to the same problems as CFL ballasts (more electrolytic caps near heat-emitters.)(The electrolytics in question typically rectify the 60cycle mains to HVDC, prior to a fancy (or not) switching circut that does voltage conversion and/or current limiting. I don't think ceramics are a viable alternative there.)(An interesting idea is to convert to rectified HVDC in the fixture, using nice big caps far away from most of the heat. That should reduce some heating in the lamps themselves (ripple current in the caps), prevent cap failures from being so noticeable (the following circuits would get DC anyway), and avoid the emissions problems that might be caused by long wires leading from the electronic ballast to the lamps. And it would be backward compatible with existing lamps that have full-wave rectifiers anyway. And it wouldn't even add a lot of cost to the fixture. You could even do a magic snake-oil "extend the life of your CFL bulb" cord-wart thing that might actually work. PROVING that it works might be a problem. And I suspect that there are all sorts of regulatory issues involved (sigh.))

author: IanB
author_rank: Super Contributor
timestamp: January 23, 2012, 06:53:52 pm
content: I've noticed that all the CFL bulbs on the shelf say "not dimmable", and all the LED bulbs I've looked at say "dimmable". So I'm not sure what circuit topology the LED bulbs use but I suspect it is very simple. If the circuit tried to regulate power to the LEDs it would fight against the dimmer switch.The LEDs I've seen are in the $15-$20 price range if not more, and that seems a bit high for uncertain quality and technology (even with a brand name like Philips).

author: wkb
author_rank: Super Contributor
timestamp: January 23, 2012, 07:11:04 pm
content: Yup, mine are definitely stamped "non-dimmable"

author: grumpydoc
author_rank: Super Contributor
timestamp: January 23, 2012, 10:34:16 pm
content: The LED lamps go "pop" as well - they also cram electrolytics into a small, hot, space.Here's one I fried (well, it fried itself) earlier - a 3x3W GU10 jobbie. Don't know what died exactly - there's a dead short across the bridge output. I assumed that it was the cap but that's still reading OK. Won't know whether it's gone high resistance until I build an ESR meter but it's reading 4.6uF. If you look carefully you can see where the track on the mains side of the bridge tried to act as a fuse. Not sure what the blue thing is - PTC or fuse, presumably, but it's insides are liberally blown all over the electronics.Active components, for interest, are - MB6S 0.5A BR, 9910B LED driver, SM2N60 n-channel FET, and a MURS160T3G power rectifier (marked U1J). Oh and a zenner of some sort but being SMD all I have to go on is the Z1 label on the PCB printing.Circuit looks straight off the 9910B data sheet.The LED chips themselves are OK so I'm just trying to figure out how best to reuse them.

author: FenderBender
author_rank: Super Contributor
timestamp: January 23, 2012, 11:08:16 pm
content: Yeah I guess that's what happens when you put some cheapass parts on a cheapass PCB in a cheapass design. For pete's sake, if you are going to use electrolytics in ANYTHING, please use ones that actually have a distinguishable name on them. Or better yet, don't use them at all, if possible.Grr. Bean counters.

author: mariush
author_rank: Super Contributor
timestamp: January 24, 2012, 12:28:22 am
content: Here's two CFL lamps that are sold here in Romania for about 2-3$ a piece.... 20-22w lamps.No surface mounted parts on their back sides so only front pics.The first has about a third of the white tube black so I guess that's what failed... on the second I guess a diode is busted or the capacitor.. I don't trust them enough to waste my time trying to fix them....Oh yeah... as I write this, I remembered posting on another forum another lamp I opened that got my attention with the Pchicon capacitor...thought it's a lame attempt to fake Nichicon. But at least the design seems a bit more complex and I think that's even a thermal protection near the transformer.

author: Simon
author_rank: Unknown
timestamp: January 24, 2012, 07:14:21 am
content: Quote from: SeanB on January 22, 2012, 06:26:54 pmagreed, don't complain if you buy rubbish

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 24, 2012, 07:26:11 am
content: Quote from: Simon on January 24, 2012, 07:14:21 amQuote from: Mechatrommer on January 22, 2012, 07:04:46 pmwhat is better quality brand? i have bunch of philips flou's that died, almost the same circuit as posted above. now i have in stock many type of brand, each time i replace, i will write the date on it, so i can check which one will last longer than others. your recommendation may speed this process up dramatically.

author: Simon
author_rank: Unknown
timestamp: January 24, 2012, 07:50:23 am
content: most CFL's in supermarkets are rubbish. I tend to try and buy online the ones that are 3500-5500K and cost a bit more and hopefully better built as they are for the more concious consumer

author: grumpydoc
author_rank: Super Contributor
timestamp: January 24, 2012, 07:59:56 am
content: QuoteSometimes there isn't much choice - the 3x3W GU10's - which are the only ones which approach a 50W halogen in brightness - were, for a long time, only available from one supplier in the UK.Even if people want to buy better quality how does the average person know - most won't go online for quality - maybe to get a cheaper price, but probably not for quality and even if they did there's no guarantee that a "brand name" is any better than "no-name rubbish" when it's taken apart.

author: Balaur
author_rank: Unknown
timestamp: January 24, 2012, 10:07:05 am
content: I've actually repaired one of my bulbs. And it was a Philips, no less.One of the ceramic capacitors failed in a very obvious way (hole in the package). I've replaced that one and still works after two years.BTW, if you ever need HV transistors (ex: for Nixie clocks), CFL bulbs are a very good source of them.Cheers,Dan

author: BravoV
author_rank: Super Contributor
timestamp: January 24, 2012, 10:26:16 am
content: Someone from Czech Republic did an intensive teardown & documenting the circuit at varous types ->http://www.pavouk.org/hw/lamp/en_index.htmlWorth a place in your bookmark imo.

author: RJSC
author_rank: Regular Contributor
timestamp: January 24, 2012, 11:52:40 am
content: I like to fix them, not so much for the cost, but for the joy that saving something from going to the trash (landfill, incinerated/etc) gives me.This wasteful society that makes things designed to fail in order to sell more disgusts me.I've fixed a dozen and I've never seen the electrolytic capacitor die!Its usually the tube died, or much more frequently, a very crappy ?polyester? green capacitor, supposedly 1000V that sits between the two filaments that shorts out!It's function is to pass current through the 2 filaments during the heating phase, and then, the frequency changes, the tube presents a lower impedance and current starts to flow trough the tube and not trough the filaments and capacitor.When it fails shorted, the current is always flowing trough the capacitor and filaments, and if it's left on, it leads to the blackening of the end of the tubes because of filament burn out.These are the capacitors I was talking about:You guys blaming the poor electrolytics... It's not always them!Do you believe me if I tell you I have fixed a laptop motherboard with a shorted ceramic capacitor? Who had thought, right?I've carefully dis-soldered every electrolytic from the bus and the sort was sill there!Then I remembered of the ceramics! bingo!Usually on old CRT TV I've fixed, its a resistor or a ceramic capacitor damaged, more rarely it was an electrolytic,It goes against what I've read everywhere: "electrolytics are the fist to fail", but it's my personal experience.Please take some time to watch this, there is proof that manufacturers of incandescent bulbs agreed to intentionally shorten their lifespan.As for the CFLs life, I wouldn't be surprised if something like this is going on with CFL's as well.

author: Mechatrommer
author_rank: Super Contributor
timestamp: January 24, 2012, 01:31:21 pm
content: we (i) need some info how actually the circuit works. any idea/link?

author: RJSC
author_rank: Regular Contributor
timestamp: January 24, 2012, 01:36:24 pm
content: The link above (http://www.pavouk.org/hw/lamp/en_index.html) with the teardown also explains how the circuit works, in a slightly broken englishQuote

author: wkb
author_rank: Super Contributor
timestamp: January 24, 2012, 01:51:07 pm
content: Quote from: RJSC on January 24, 2012, 11:52:40 amThese lookveryfamiliar...

author: RJSC
author_rank: Regular Contributor
timestamp: January 24, 2012, 02:14:34 pm
content: Quote from: wkb on January 24, 2012, 01:51:07 pmPlease elaborate a bit... I'm not getting it.Where else are they famous for failing?

author: wkb
author_rank: Super Contributor
timestamp: January 24, 2012, 03:50:05 pm
content: Quote from: RJSC on January 24, 2012, 02:14:34 pmThese are the same caps I found in the broken lamp that started this whole thread.

author: RJSC
author_rank: Regular Contributor
timestamp: January 24, 2012, 04:42:07 pm
content: Quote from: wkb on January 24, 2012, 03:50:05 pmI haven't got time to read the whole thread in detail, so, excuse me if you already fixed it, but...If you still have the lamp, can you test the capacitor between the filament poles for a short?

author: westfw
author_rank: Super Contributor
timestamp: January 24, 2012, 08:02:39 pm
content: Interesting. I wouldn't have suspected the mylar caps (what's to do wrong?), but I've definitely seen swollen and even burst electrolytics as well.There are CFL reference designs out there, especially from the vendors offering ICs for circuits more complex than the cheapest. (there ARE dimmable CFLs, for instance.) IFR has a bunch of products:http://www.irf.com/technical-info/refdesigns/lightingkits.htmlPeople who dismiss CFLs for their "manufacturing expense" haven't thought too much about what goes into manufacturing incandesant bulbs, I think. I mean: tungsten wire doesn't exactly grow on trees!

author: wkb
author_rank: Super Contributor
timestamp: January 24, 2012, 08:05:54 pm
content: Quote from: RJSC on January 24, 2012, 04:42:07 pmSorry, it went to the recycling bin. I still have the 2nd one, unopened. Plan to take that to the shop I bought it from and do some whining. Found a carton of a smaller version of the same brand, and they promise 5 year / 5000 hours....