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Sherlock Ohms

Monitor Goes Dark Over Cheap Components

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Shelly
User Rank
Iron
Re: cutting one corner too many.
Shelly   5/23/2012 9:19:35 AM
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The same exact issue happened to me with TWO Samsung LCD televisions!  I have a large LCD TV in my living room, and it started to take minutes, instead of seconds, to turn on.  This wasn't too big of an issue until it started to take upwards of 15 minutes.  I did some research and found that the power supply capacitors would blow (four of them).  I replaced them and all was well.

One year later, the small TV in another room began to show the same problem!  I immediately tore it apart and found the caps on the power supply bulged.  I am a mechanical engineer, so it was quite interesting for me to fix this (thanks to the internet).  The toughest part, especially on the small TV, was fitting the larger caps into the small space.

Charles Murray
User Rank
Blogger
Re: cutting one corner too many.
Charles Murray   5/22/2012 7:59:38 PM
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Here we are again, discussing a subject that comes up on our website almost on a daily basis. I'm amazed that the cost of a few capacitors is worth the damage it causes to Acer's reputation. If there are websites dedicated to problems like these, the situation must be pretty bad.

gsmith120
User Rank
Platinum
Re: cutting one corner too many.
gsmith120   5/22/2012 7:36:57 PM
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Rob, you read my mind.  That's exactly Rob, you read my mind.  Counterfeit parts are exactly what I was thinking; they are becoming a major problem.  This really bothers me especially since I deal a lot with mission critical systems.

Tim
User Rank
Platinum
Re: cutting one corner too many.
Tim   5/22/2012 7:23:03 PM
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I like the idea of the care package for the end user. I once purchased a DIY bookshelf that contained two hardware kits and a note that read to only use the one specially marked hardware package because the screws were a better design. The rework for the faulty screws was open the box and add a new bag and a note then retape the box and hope for the best.

pcan
User Rank
Iron
Re: cutting one corner too many.
pcan   5/22/2012 4:25:32 PM
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On a previous job, I worked in the technical department of a importer of LCD TV's and computer monitors. The computer monitor product line was manufactured by a well known Taiwan OEM manufacturer with good reputation and big name clients, and branded with our company logo. Technical documentation, EMC test and product samples - everything was perfectly fine. After 8 months and truckloads of monitors already sold, the number of field returns started to rise. In the summer, it became a deluge; almost every single monitor broke on the field. The power supply had faulty capXon electrolytic capacitors. On closer examination, the power supply design turned out to be questionable. The faulty capacitors were extremely close to heat spreaders, and they produced high amount of heat themselves. They may have worked well in a traditional full bridge power supply, but certainly not in a high-frequency switched mode power supply. A comparison to the schematic diagram of the switched mode controller chip revealed that the power supply manufacturer removed all the current limiting components except the main safety fuse, and substituted a 1000V rectifier diode with a 200V rectifier. The result: a minor power surge or the increased load caused by the degrading capacitors would open the safety fuse. This was supposedly a quality product from a reputable supplier. The company management was so upset that completely abandoned this market and closed down the business unit. The last container full of soon-to-be broken monitors was sold at scrap price to a broker that shipped them to central Africa. We enclosed a courtesy gift: a box full of quality replacement capacitors and complete instructions for the rework. I keeped for internal company use about 50 monitors. After replacing the capacitors, they still work after almost 5 years.

Rob Spiegel
User Rank
Blogger
Re: cutting one corner too many.
Rob Spiegel   5/22/2012 2:19:05 PM
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This makes me wonder whether the components that failed were counterfeit. Counterfeits can be disguised very well these days. Counterfeit components woud certainly explain the high failure rates Naperlou describes.

nauzad
User Rank
Silver
Re: cutting one corner too many.
nauzad   5/22/2012 1:44:48 PM
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Just looked up some old references. The caps originally on the board were CapXon's rated to 85ºC if I recollect correctly.

rjnerd
User Rank
Iron
Re: No derating?
rjnerd   5/22/2012 10:44:42 AM
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Its a 5v circuit, and the cap is labeled 6.3 volts.

Nancy Golden
User Rank
Platinum
Internet for Troubleshooting
Nancy Golden   5/22/2012 10:39:25 AM
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Looks like you did a great job - that is one thing I love about the advent of the internet. It has become a valuable resource for troubleshooting. I have had issues from my video camera to my garage door opener and plugging in the problem has brought not only answers, but video demonstrations for the fix on You Tube! I love it when it is as simple as replacing a cap or two. I would have thought the same thing - that there may be something causing the caps to blow. But even if it isn't a matter of cheap materials but heat stress or some such thing that becomes an issue over time - at least you'll know what to do. Hopefully Acer has caught on and fixed the problem. It's funny - when I called Sony about the defect occurring with my video camera, they said they had no prior knowledge of that type of failure - yet a simple search on the internet indicated at least fifty or so other folks experiencing the same issue!

tekochip
User Rank
Platinum
No derating?
tekochip   5/22/2012 9:51:39 AM
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Do you know the voltage rating on the caps? I wonder if they were pushing them at the edge of the specification with no derating, you know a 6V capacitor on a 6V circuit.


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