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fake PC supplies

Discussion in 'Electronic Design' started by Adam. Seychell, May 23, 2005.

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  1. I'm recently seeing more cheap PC supplies on the market which appear to
    be fake, in that the clammed output power not impossible for the size of
    parts inside. e.g I have a 500W "Shaw" brand ATX supply, and its output
    inductor uses a piddly T106 (26mm OD) core. The 5V is specified at
    35Amps yet the output inductor winding is 2x1.2mm diam wire and the
    rectifiers for the 5V is a 15Ax2 Schottky device. This is typical for
    these very cheap power supplies. Similarly the 12V @ 18A output uses
    2x8A diode (STPR1620).

    I've also seen several other PC supplies that have completely omitted
    EMC components, and simply used wire links where the CM inductors are
    meant to go. Some PC supplies I've come across have even used standard
    ceramic/polyester capacitors in place of the Y and X2 rated safety

    How do they get away with this ?
  2. Bill Bailley

    Bill Bailley Guest

    They can, and they will, until these underrated and dangerous PSUs generate
    sufficient fires/casualties/deaths to trigger a judicial/coroners enquiry. A
    negative finding will cause ALL the companies who make the PSUs to
    disappear, and the importers/resellers to wave their certified
    performance/compliance paperwork as a shield against prosecution.

    Money IS the root of all evil!
  3. Set up a Holding Company, the Holding Company Import loads of chinese
    ripoffs and sell them to a group of Distributers in the form of Limited
    Companies, who, in turn, will put whatever sticker on that sell the unit -
    nevertheless they do not make much profit because the markup is with the
    Holding Company.

    Eventually, someone/something gets hurt and Distributor gets sued;
    Distributor goes bankrupt; Holding Company gets to keep the profit because
    *it* never did anything wrong, it just Imported the stuff.

    *WHY* They can get away with this is the Interesting Question!
  4. Kelvin Chu

    Kelvin Chu Guest

    Hmmm, would you have brands in mind that are bad/good?

    So, should we be buying those Antec Power Supplies (TruPower or soemhting
    the name is I think)?
    But they are so expensive!!! (well, 2-3 times cost of cheap Power Supply...)

  5. R Adsett

    R Adsett Guest

    The love of money is the root of all evil!

    The quote makes more sense when it's complete. Also it's "The proof of
    the pudding is in the tasting" not "The proof is in the pudding"

    Robert (feeling pedantic today)
  6. Rich Grise

    Rich Grise Guest

    By using insanely high switching frequencies. Ten or fifteen years ago,
    I had a client who wanted to build a 24V, 30A switcher for an on-board
    wheelchair battery charger; three months later we abandoned the project,
    because even the guys from the company who sold the magical chip weren't
    able to teach me switcher design. The chip was rated for 1 MHz. A
    MEGAHERTZ! In a SWITCHER! =:-O These days, I wouldn't be surprised if
    they're approaching gigahertz switching frequencies - heck, look at
    microprocessors these days, that are big enough to be their own antenna!

    Have you seen any of these magical mysterious power supplies kill anybody,
    or even let the magic smoke out?

  7. Pooh Bear

    Pooh Bear Guest

    a) Probably because no-one actually *needs* a 500W power supply and the
    dodgy suppliers know this.

    b) Because it's possible to cheat and lie. Enron did this rather
    dramatically for example.

  8. WRONG!!! WRONG!!! WRONG!!! WRONG!!! WRONG!!!!!!!!!!!!!!!!

    Money is merely a scorekeeping device. It's inanimate. It just sits
    there, until somebody uses it to buy something. My Mom, bless her, was
    very specific in teaching me that it's the LOVE of money that's the root
    of all evil.

    LOVE of money is the root of all evil.

    That's LOVE of money as a replacement for love of life, love of
    pepole, love of love, love of reality, and so on.
    Rich Grise
    First Member, Church of the Neodruid

    In truth, it's denial that's the root of all evil, but that's advanced
    metaphysics - for further information, please visit
  9. Tom's Hardware has tested some PC power supplies.

    Inadequate and Deceptive Product Labeling:
    Comparison of 21 Power Supplies

    Test Results In Detail

    Let's not beat about the bush here. The 21 power supplies we tested
    are rated by their manufacturers at between 300 and 520 watts. Our
    tests showed, however, that only 15 of them actually met their


    Of course the good ones can cost more than a whole cheap PC...

    Best regards,
    Spehro Pefhany
  10. Guy Macon

    Guy Macon Guest

    Many years ago I had a no-name PC Power supply take out a motherboard,
    both hard disks, all the cards, and even the keyboard. Since then
    I have never powered up a new system without first replacing the PS
    with one from PC Power and Cooling, which I consider to be the maker
    of the best PC power supplies available.
    ...and my data is worth more than both put together. :)
  11. My favorite misquote is "Pride goeth before a fall". The correct phrase
    is "Pride goeth before destruction, and an haughty spirit before a fall"
    (Proverbs 16:18).
  12. Even if you don't get the fireworks you can get crashes, data
    corruption etc.. See the above article which had one supply dropping
    the 12V line to < 6V. I'm sure the typical $99 200GB drive is going to
    love that.
    Yes, even the hassles of restoring a system that has fried itself is
    probably worth more. Assuming you have full backups.

    Best regards,
    Spehro Pefhany
  13. Mike Monett

    Mike Monett Guest

    Guy Macon wrote:

    I had the same thing happen. Fortunately I keep good backups so I didn't
    lose anything.

    But even the best power supply can fail, or an external device could
    develop a short between voltages. I've been thinking of a simple crowbar
    that could be added to the +12V and +5V supplies. Have it short the
    voltage if a failure raises the voltage above a limit, and plug it in a
    spare drive power connector to prevent damage if anything goes wrong.

    I don't know how power supplies react to a short. If they respond by
    trying to increase the other voltages, it mmight be necessary to crowbar
    all the voltages at the same time. I'd probably do it just to be on the
    safe side.

    One problem would be indicating which voltage triggered the circuit so
    you could troubleshoot it. This might take a small battery powered
    circuit to store the conditions at failure, and a switch to light the
    corresponding led to examine the failure.

    This could be made real cheap. Anyone know a source for inexpensive 50A
    or 100A scr's?

    Mike Monett
  14. Some (most?) PC power supplies already have crowbar or some other
    kind of overvoltage protection built in. For example (this is a beefy
    server supply):

    See table 3.5.2.

    Here's another:

    In fact it's required in the Intel's Design Guide:\specs\ATX_ATX12V_PS_1_1.pdf

    See section 3.4, although the Enermax supply does not meet the
    overvoltage specification on the 3.3V line.

    I always liked section 3.1.5 as well. What exactly constitutes
    "excessive smoke", I wonder. ;-)
    Teccor has some 50A SCRs in TO-3P for about $5 US each one-off (only
    about $1.70 for 40A in TO-220, so much better value). Much bigger and
    you're probably into stud package and more money.

    Best regards,
    Spehro Pefhany
  15. Ian Stirling

    Ian Stirling Guest

    I wonder about a 'gentler' way.
    If you simply disconnect the main energy storage cap, then the supply
    won't stay pumping power into the output caps for more than a few
  16. Franc Zabkar

    Franc Zabkar Guest

    Read about my experience with a Deer 170W PSU masquerading as 400W.

    - Franc Zabkar
  17. Mike Monett

    Mike Monett Guest

    Ian Stirling wrote:

    Yes, I as thinking along the same line. What about a separate unit that
    monitors the voltages, crowbars them in case of a fault, and removes
    the ac power to the computer?

    As Speff points out, modern supplies are supposed to have the crowbars
    built in. However, Win 3.1 and Win 95 run fine on older computers, so
    they still have plenty of useful life. For example, I use Win 3.1 for
    internet access and have zero problems with trojans, viruses, popups,
    etc. They won't run on my system. Also have zero problem with upgrades
    breaking things. They don't exist:)

    Mike Monett
  18. Mike Monett

    Mike Monett Guest

    Thanks, Speff. The Teccor 40A scr looks very good.

    Although the newer supplies may already have protection, many older
    computers still have plenty of use. For example, I log on the web
    with a 200MHz machine running Win 3.1, and have zero problems with
    viruses and trojans. They simply won't run. I use Win 95 on a 166MHz
    machine to view pdf files that need Acrobat 4, and my main computer
    is 450MHz running Linux. Each computer needs a backup, so I am
    looking at a triple boot machine running 166MHz. I also use several
    other cpu's for process control.

    This gives a number of machines without protection, and I have
    already lost two due to power supply failure. So I'm thinking of a
    small ac-powered unit that crowbars the voltages and removes the AC
    to a faulty supply. A 40A scr probably won't even need a heat sink:)

    The Intel failure section is hilarious. I copied it below for those
    who don't have the time to download it:

    3.1.5 Catastrophic Failure Protection

    Should a component failure occur, the power supply should not
    exhibit any of the following:

    - Flame
    - Excessive Smoke
    - Charred PCB
    - Fused PCB conductor
    - Startling noise
    - Emission of molten material
  19. Pooh Bear

    Pooh Bear Guest

    With the exception of *startling noise* - all that is covered by IEC60950.
    Or UL1950 in your case.

    Nah - that's 'user notification of failure'. ;-)

  20. Mike Monett

    Mike Monett Guest

    Do you have a copy of UL1950 or IEC60950? According to this site, IEC60950
    is $337.48 USD:

    If you don't have copies, do you have another reference that discusses
    failure protection?

    Mike Monett
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