Cheap Electronics Suck!!!

Discussion in 'General Electronics Chat' started by tom66, Mar 21, 2011.

  1. tom66

    Thread Starter Senior Member

    May 9, 2009
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    Okay, I have this cool Advent 200Mbps Powerline Ethernet adapter. This basically lets you use the power lines in the house to send data from computer to computer. These were given to me new in the box as the person had wifi installed and no need for them any more. Well the wifi in my room is poor so I decided to put them to use.

    One thing always bugged me about it was that it always ran INSANELY hot during operation. Around 70°C on the case, I measured it with an IR thermometer. I would have thought that Advent would have designed the device to therefore cope with this... apparently not.

    After about 2-3 months of use, the adapter does not work any more. If left plugged in the green power LED flashes occasionally, but it doesn't do anything useful. It no longer registers as an ethernet device according to the computer.

    [​IMG]

    So, I open it up and lo and behold - as expected, the fault is a cap which has gone pop. A cheap "JACKCON" cap, almost like planned failure. They knew it would fail with such a cap in just a short amount of time. Well, unlike the majority of users, I am technically competent to repair this.

    [​IMG]

    But, the main question is why on earth it was running so hot anyway? Why would it? The design is interesting. Two boards stacked upon each other.

    [​IMG]

    The bottom board has an BGA packaged ARM processor (for a reason I cannot think of - why on earth are they using a processor in the first place? There are plenty of PoE chips which do the whole show without that being required), a REALTEK ethernet chipset (probably for PoE), two memory devices (one on the top and one on the bottom), some misc. power circuitry and the switching mains power supply. The top board has the status LEDs, and some misc circuitry. I suspect the top board has some of the receiving circuitry moved on to it to reduce the size of the entire device. I cannot imagine this drawing any more than 100mA continuously and the power supply is more than big enough to dissipate that amount of heat. The power supply controller - TNY276PN - is rated up to 5W - and is marketed as energy efficient. The heat is definitely coming from the supply and is very likely to have caused the cap to pop. I suspect it has +5V and -5V rails as the other cap is intact. To give it a chance, I'll replace both with a 1000u 10V Panasonic capacitor, a pack of four costs me only £1.50 - and that's on eBay, where prices are massive.

    I hate cheap electronics, but the thing is - these adapters weren't cheap! They were originally about £120 (for two.) I can't imagine a slightly more expensive quality rated cap would have failed in any where near the time and cost much extra. But they know that - they want you to throw them in the trash and buy a new one. Maybe you'll blame the failure on a "power surge" or something like that, then buy them again. Or whatever you do, even if you just throw them out, you have contributed to environmental waste.

    I have another one of these adapters, for the downstairs (you require two for a link.) Any bets on when that one will go?
     
  2. R!f@@

    AAC Fanatic!

    Apr 2, 2009
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    That's funny, I can't seem to find any component that would generate the said amount of heat. Try fixing it first. Run it open, use the IR to locate the source of heat.
     
  3. tom66

    Thread Starter Senior Member

    May 9, 2009
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    I have a suspicion it's the SMPS transformer. After turning it off to take it apart that was hot enough to burn my finger. Given that it is very close to the blown cap, it's also possible that it heated that up enough to cause the failure there. If not that, it could be the switcher chip (the DIP8 with the missing pin in the bottom center of the supply), or the big catch diode (which seems massive for the current requirement.)

    I can't figure out why this adapter needs so much current. Perhaps it has to do with modulating the mains for the data transmission.
     
  4. bribri

    Member

    Feb 20, 2011
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    oh i'm sure they could guess it would fail.
    these days you can buy caps rated @ 500 hours : /

    but do they both run so hot?
    ...operating at u.k. voltage rather than 110 shouldn't make a heat difference i guess....

    a neat device though : )
    i'm reminded of a t.v. program in the 1980's where a dude was demoing how he could remote control the lights on different circuits in his house... with an apple IIe and no extra hardware (if i remember rightly)
     
  5. tom66

    Thread Starter Senior Member

    May 9, 2009
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    It's a universal input device. It's slightly less efficient at 115V than 230V actually.
     
  6. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    The whole device is quite strange, is the ethernet port capable of gigabit operation? I don´t see any reason to produce something capable of 200Mbps with only 100Mbps uplink, but anyway the two chips are needed for decoding ethernet and somehow modulating it to send the packets over the power line.

    Can you read the name of that dip8 chip?
     
  7. tom66

    Thread Starter Senior Member

    May 9, 2009
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    Personally, I suspect that it's actually a 100 Mbps device, but they're using the SRAM's on the board as memory for some kind of cache or burst transfer. Maybe it can transfer at 200 Mbps in bursts. Either way, it boils down to marketing. Just like the 108 Mbps 802.11G devices you can buy.

    It's a TNY276PN.
     
  8. bribri

    Member

    Feb 20, 2011
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    mmm, so what would cause that transformer to heat up so much?
    bad case of harmonic resonance?
     
  9. tom66

    Thread Starter Senior Member

    May 9, 2009
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    Perhaps it's just undersized for the power supply. Maybe the supply is hideously inefficient.
     
  10. Audioguru

    New Member

    Dec 20, 2007
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    My cable modems also do not last long. They get hot.
    Every two months I simply take the defective modem to the local cable TV (DVD rental) store and the pretty young lady (WOW!) throws it in the garbage that is loaded with many more of them. They don't bother fixing them anymore.
     
  11. Kermit2

    AAC Fanatic!

    Feb 5, 2010
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    Could it be the ceramic of the inductor? If it has somehow become energized with a bare copper connection in the winding, the electrical resistance of the device itself could be causing the heating.

    ALSO check the inductor core of the transformer with a volt meter while it is in operation.
     
  12. tom66

    Thread Starter Senior Member

    May 9, 2009
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    It's sad to what extent electronics have become - throwaway items. I had an old Philips CRT TV a few years back. It was nearly 15 years old according to the date of manufacture. It worked perfectly, but started getting lines across the picture (grey lines, suspect a HV fault), probably due to a fault with one of the filter caps. But the fact of the matter is, it had a hard long life, and it was built to last. Same for my scope. 18 years without an issue, started going funky, can of compressed air to clean it out and I expect many more years from it (very well designed.) It pissed me off that this lasted barely 3 months before going pop. And it's certainly not a limited trend. My mum's kindle lasted only 3 weeks before the display went. It seems like a common problem, not related to force or damage, and Amazon usually replace them - but at what cost??
     
  13. tom66

    Thread Starter Senior Member

    May 9, 2009
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    I powered it up with faulty caps. Both caps have 1.8V across them. Power and ethernet LEDs glow dimly. Nothing else works. I'll check it later when I fix the caps, but it's possible the cap going took something else out (if the supply became unstable for example.)
     
  14. magnet18

    Senior Member

    Dec 22, 2010
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    I personally love the quality control sticker right next to the busted cap, the irony is overbearing :p
     
  15. tom66

    Thread Starter Senior Member

    May 9, 2009
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    I somehow wonder if it's just a marketing tactic they have it on the device itself, "wow it must be good, it's passed QC!!!!111one!!eleven1"
     
  16. magnet18

    Senior Member

    Dec 22, 2010
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    Marketing INSIDE something?!?
    They really will go to any extent nowadays, wont they :rolleyes:
     
  17. tom66

    Thread Starter Senior Member

    May 9, 2009
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    No, there's a sticker on the outside. That would be a bit much. :p
     
  18. bribri

    Member

    Feb 20, 2011
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    'designed for the dump' has officially been promoted from mild side-effect to full scale disease of our techno-fetishistic hyper-modern culture. the innovation / obsolescence spiral of feigned nostalgia and empty optimism has become a vortex.
     
  19. magnet18

    Senior Member

    Dec 22, 2010
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    Poetry... and every word of it true :(

    I'll say, considering that if it never breaks no-one would ever open it in the first place.
     
  20. tom66

    Thread Starter Senior Member

    May 9, 2009
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    This throwaway culture needs to stop. If we are to prevent inevitable damage to our environment.

    I'm getting into making electronics. If I ever become successful, my #1 item will be to make reliable electronics. I have a theory that in the end, you'll make more money because you'll have a better rep. But do people look so far as that?
     
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