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Crappy mains adapters & crappy designs

Discussion in 'Electronic Design' started by Nico Coesel, Feb 14, 2007.

  1. Nico Coesel

    Nico Coesel Guest

    I feel like ranting and I think it is on-topic so here it goes:

    One of the things I start to hate more and more is when potentially
    nice equipment fails because it wasn't designed to deal with something
    trivial like a mains adapter dying.

    Currently I have 4 dead wireless access points (from a very
    respectable firm, not some cheap-ass shit) dead on the bench here. All
    because their mains adapters died.

    I posted a picture of a disassembled adapter here:
    http://selvi.nctdev.nl/adapter.jpg

    Notice the burn marks on the rubber foam which was placed between the
    casing and the solder side of the PCB.

    I suspect the adapters started to provide DC pulses which somehow
    partly erased the flash memories in the wireless access points.
     
  2. John Larkin

    John Larkin Guest

    We sell a few little boxes that are powered from a 12-volt wart. We
    always start with a polyfuse, followed by a 15 volt transzorb, which
    also gives reverse polarity protection.

    John
     
  3. Looking at these I suspect they are using a series cap to reduce the voltage
    to the transformer.

    The WAPs no longer work with a good PS?
     
  4. Ecnerwal

    Ecnerwal Guest

    More to the point, the equipment might be nice, but management decided
    that a power supply was a commodity item to be sourced from China -
    though I suspect your entire units were made there.

    I have a very expensive, now very obsolete, US-made networking box that
    does some esoteric processing which lets us run a segment of network
    over a wire that would not otherwise run it. One day it stopped working.
    I eventually figured out that the cheap-Chinese power supply had crapped
    out (this was not overly obvious since the lights were still on, as it
    was not dead on all 3 voltages).

    I pulled an old clunky linear supply from the junkbox and spliced it
    into the connector, even though the unit was still under warranty. If I
    had gotten the warranty replacement, it would have been the same crappy
    quality, and my tolerance for that is limited on boxes that cause much
    crying out and gnashing of teeth when they break. I did inform the
    company of what I had done, and why, but got no response from them.
     
  5. Joerg

    Joerg Guest

    With all due respect that does not look like stuff from a respectable
    firm. There are wall warts from reputable sources such as Condor/Ault
    but it seems this "respectable firm" might have cut a corner here and
    saved a buck.

    Check out SMC. I've got their Barricade router here and it has a
    built-in switcher. Nothing gets hot, ever. It's totally cool to the
    touch. Imagine, a built-in power supply. Wow. What a concept. Guess
    people slowly figured out how grandpa's tube radios were designed and
    why they last so long.

    Oh, BTW, that Barricade router has a full metal enclosure. None of this
    plastics stuff. Byu some real industry-grade gear and you shouldn't have
    that problem. If it has a wall wart look for something better. If it has
    a cheap wall wart, run.
     
  6. jasen

    jasen Guest

    what's the 400V electrolytic capacitor for then?

    As I read it the small yellow box and the tranformer looking thing are a
    capacitor across the input and a common-mode choke, the large yellow box
    is the transformer
     
  7. Terry Given

    Terry Given Guest

    yep.

    I've pulled a fair few of these to bits. the construction ranges from
    excellent to appalling.

    The trick is to stick to a reputable manufacturer.

    The problem is without a hacksaw, you cant see what they are like!

    Meanwell make reasonably good stuff.

    Cheers
    Terry
     
  8. How about doing us all a favor and naming names?
     
  9. Guest

    Not Cisco Systems (Linksys)?
    I plug mine in a good quality powerstrip that has surge protection and
    all the bells and whistles no problems so far...
     
  10. mpm

    mpm Guest

    And it's only going to get worse with new government standards for
    higher efficiency wall warts!
    Unless of course, these same Standards weed out all the incompetent
    designer wannabees.
    But I doubt it.

    I think the California law goes into effect this year??
    -mpm
     
  11. Eeyore

    Eeyore Guest

    Bwahahahahahahhaha
     
  12. Nico Coesel

    Nico Coesel Guest

    Well, in fact the 4 units are from Linksys placed in different
    locations in a building on different mains groups (2 powered from a
    UPS).
     
  13. Nico Coesel

    Nico Coesel Guest

    I tried that, but no go.
     
  14. It looks too small for 50/60 Hz unless it's an SMPS in which case it gives
    me no confidence.
     
  15. joseph2k

    joseph2k Guest

    Of course, if you know your mains are crappy, you should have upstream
    protection for the wall warts.
     
  16. joseph2k

    joseph2k Guest

    That's a really crappy UPS that let something through that wasted something
    dowqnstream.
     
  17. Joerg

    Joerg Guest

    Or crappy power supplies that barely hung on and then collapsed. I have
    seen some horrible "designs" where stuff had turned brown just from
    normal operation. Others had 300V devices on directly rectified mains
    and were marketed in Europe, meaning their ratings were exceeded even
    under perfectly normal line conditions. Then there was one that got
    freaking hot and the mfg said it was normal. One fine day the ambient
    temp went a wee bit above 30C and ... POOF.
     
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