Video: Teardown of a cheap, failed linear power supply - Page 1
Forum section: electronics / general

author: w2aew
author_rank: Super Contributor
timestamp: March 13, 2014, 09:45:51 pm
content: In this video, I break open and teardown a cheap linear power supply that failed a moments after being plugged in for the first time.

author: Fluxed Matter
author_rank: Regular Contributor
timestamp: March 13, 2014, 10:09:34 pm
content: +1 Great video I loved how you popped it open with the hammer. Too bad you did not hook it up to a scope so we could see how bad the waveform is.

author: deth502
author_rank: Frequent Contributor
timestamp: March 13, 2014, 10:10:13 pm
content: im surprised it stayed so close to spec even after it popped. under 5 ohm i probably would even suspect it if i was troubleshooting something (meaning a large circuit, not this supply). normally when i see high esr they are in the 3 digit ohm range.not that the top wasnt a dead giveaway, but i would have expected the measurements to be much further off.

author: Kjelt
author_rank: Super Contributor
timestamp: March 14, 2014, 08:58:01 am
content: very nice video!Too bad you already cut the wire because replacing that terrible green chinese garbage elco with a decent Rubycon or Nichicon 105C would have been easy.I have and had the same problems with chinese power supplies. I bought a decent amount of SMPS with a firm called Pollin in Germany and one after the other failed and when the elco's failed more components were dead.Now before using them I first replace the elco's and resolder half the boards solder connections.

author: HighVoltage
author_rank: Super Contributor
timestamp: March 14, 2014, 12:13:21 pm
content: @w2aewI wonder: Are there any good quality electrolytic capacitors that will last like 20 or 30 years or even longer?Why is it that in the last few years, so many capacitors fail in all kinds of equipments, including high end scopes from Tektronix or name brand monitors like Samsung. It is hard to believe that they all do this on purpose to sell new parts and equipment.

author: Len
author_rank: Frequent Contributor
timestamp: March 14, 2014, 04:52:46 pm
content: Quote from: HighVoltage on March 14, 2014, 12:13:21 pm(I'm not him but I'm gonna answer anyway.)QuoteI have a stereo receiver that's > 30 years old and still works fine. I haven't looked inside recently but I'm guessing that the electrolytics are still OK. Ditto for an old clock radio.On the other hand I've had several pieces of equipment purchased in the last decade fail because of bad caps.It's purely because of cheapness. The manufacturers think that if every single unit survives past the warranty period, they shoulda made it cheaper.

author: Kjelt
author_rank: Super Contributor
timestamp: March 14, 2014, 05:45:54 pm
content: Yes it is mainly price i agree BUT also quality and i think also that the person responsible for component buying is probably better in finance then electronics. I can already see that guy behind his computer: we need a 2200uF 25 V elco, hmmm rubycon 0,45$ and garbagecan brand costs 0,10$ which shall I take to get my end of the year "save 10% off spending" bonus. What do I care that it breaks after 2 years, I got my bonus. And I can also see the responsible design engineer when the samples arrive: what dickhead put garbagecan brand elcos in my design

author: Nerull
author_rank: Frequent Contributor
timestamp: March 15, 2014, 02:26:04 am
content: Counterfeit electrolytics were a pretty major problem for about a decade, from 1999-ish to 2007-ish. Someone in Taiwan stole a trade secret electrolyte formula, but replicated it poorly resulting in high failure rates. The bad formula spread to many other manufacturers. It is very common for those caps to fail after only a couple years of use, far short of their speced lifetime.The "plague" affected low and high end manufacturers alike. It was so bad that having as few electrolytic capacitors in a circuit as possible became a marketing feature.

author: Len
author_rank: Frequent Contributor
timestamp: March 15, 2014, 04:02:34 am
content: Sorry, but I don't buy that excuse any more. There are still lots of capacitors failing after 1-2 years of use, and there are certain brand names that keep showing up. That story about the mistaken formula may have been true originally but that excuse ran out years ago. These days, manufacturers who use cheap crappy caps know exactly what they're doing.

author: BravoV
author_rank: Super Contributor
timestamp: March 15, 2014, 04:43:59 am
content: Alan, thank you ! Great video, simple & straightforward !Although I personally do own a LCR meter "and" an ESR meter too, this at least to show people that you don't need a LCR meter just for simple problem like this.Its just too tiring to hear every time from those LCR Nazisthat you have to do cap impedance measurements to trouble shoot similar problem which sounds so ludicrous.

author: SeanB
author_rank: Super Contributor
timestamp: March 15, 2014, 05:52:58 am
content: You pay for lifetime. Cheap sub cent units with a lifetime that is just beyond warranty period, or 20c units that will do 5 years minimum. Bean counters choose the cheapest.

author: jancumps
author_rank: Unknown
timestamp: March 15, 2014, 06:25:52 am
content: Godwin's law proven in 10 posts.

author: johnwill
author_rank: Contributor
timestamp: March 17, 2014, 09:54:06 pm
content: I remember seeing a story about intercepted counterfeit UL labels in Miami and I suspect that stamped UL on the transformer means nothing.?

author: NiHaoMike
author_rank: Super Contributor
timestamp: March 17, 2014, 10:51:29 pm
content: A lot of cheap wall warts have output caps with just barely enough voltage rating.