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computer power supplies..

Discussion in 'Electronic Repair' started by larya, Apr 23, 2009.

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  1. Bob Larter

    Bob Larter Guest

    I used to own several ST-506s & ST-412s. Long gone now, of course.
  2. Powermac

    Powermac Guest

    I still have a few Seagate 9GB 5.25" FH SCSI drives in external boxes
    for my old AVID capture setups. I keep them around because they still
    work and are OEM to the systems.

    The problem I see with most PS supplies are cheap parts that fail when
    the fans cooling them get clogged up with cig smoke or pet hair, dust,
    etc. That and buying one that is too small for the load you are

    How did DELL and eMachines get away with small 250W max rated supplies
    in P4 3Ghz+ and Athlon 64 3000+ systems? if you added a decent gaming
    video card and an extra HD you probably had voltage issues.
  3. Hi!
    Dell underrates their power supplies *greatly*. I've never had a
    problem with one, and they seem to be pretty well made, in line with
    other quality brands.

    As an example, the 305-watt rated unit (made by Lite-On) in my
    Dimension 8300 is powering two hard drives, 2GB of installed RAM, an
    ATI Radeon X1350, two optical drives, floppy drive and a full host of
    PCI expansion cards. It has no problems, and has been doing that since
    it was new. The air coming out of it is moderately warm.

    At first it powered a 3.4GHz P4 Prescott which ran
    around the clock. Later, I switched to a 2.8GHz Northwood as the
    Prescott was good only for putting out heat sufficient to warm a small

    The eMachines supplies have two things working against them--the first
    being that in some cases they don't have working overvoltage
    protection in place. This results in motherboards getting fried. I
    haven't seen too many that I could say failed as result of running out
    of capacity anyway.

    And you could do worse, with a supply that lies about its

  4. Bob Larter

    Bob Larter Guest

    Hard disks last a very long time if you're careful to give them enough
    airflow to stay cool.
    But most people don't do that.
  5. Baron

    Baron Guest

    I have to add "Me Too" I have a genuine Apple ST405 from 1982. Four
    platter linear actuator. I don't remember how big it was, 10Mb maybe !
    I agree. Pay cheap, Get cheap !
    I'm sure that was quite deliberate ! Remember the "Warranty Void" if
    you opened the case. Often enforced by a sticker over the removable
    case panels. Huge numbers of people caused damage by fitting extra
    drives, video cards and CD/DVD burners without understanding what they
    were doing. Like everything else today... Pared down to the bone to
    cut costs !
  6. westom

    westom Guest

    Learn what engineers know and what many computer assemblers don't
    grasp. That 250 watt supply in a Dell is also called 360 watts when
    sold to computer assemblers. Neither lied. Only one is providing a
    more honest number. Latter is selling to A+ Certified Computer techs
    who need not even know how electricity works to be certified.

    Lack of technical knowledge is why so many power supply myths are
    believed by a majority. Other popular myths involve thermal compound,
    hardware damage due to heat, protectors, and shotgunning. Myths
    traceable to untrained computer assemblers. So many as to suggest why
    so much electronic and computer design must go overseas AND why so
    many engineers (probably a majority) in the Silicon Valley are now

    A choice is offered. To know only because the majority promote that
    myth. Or to know by also learning why – which means numbers and the
    underlying reasons why.

    Dell does not underrate their supplies. Overrated is technical
    knowledge of people who never first learned basic electrical
    principles and then post as if knowledgeable. That has even created a
    market ripe with power supplies that are missing essential functions.
    They are selling to the electrically naive. But then this should be
    obvious. If he does not provide the many technical reasons why - and
    numbers - then assume myths.
  7. Eeyore

    Eeyore Guest

    Unfortunately we had Micropolis 9 GB drives for Lightworks that had a fatal
    manufacturing error that consigned them all to scrap after a year or two.

    I have one ancient PC ( my old DOS box ) I've replaced the fan in twice.
    Bearing failure, nothing else.

    Probably because they are *real* watts. The Asian ones are somewhat

  8. Eeyore

    Eeyore Guest

    5MB unformatted. That's where the 5 in 405 comes from. 5 was the form factor
    - F/H 5 1/4".

  9. Franc Zabkar

    Franc Zabkar Guest

    I have a fake ATX PSU labelled as 400W, yet the Schottky rectifiers on
    the secondary side can only deliver 200W max. Although it's still
    working, I replaced it because the +5V and +12V rails were moving
    about too much during load changes, eg when my CPU cooler program
    kicked in.

    - Franc Zabkar
  10. Adrian C

    Adrian C Guest

    Westom = troll. Please ignore the patronising ramblings of this idiot.
  11. Baron

    Baron Guest

    Thanks. Its a real dinosaur by todays standards. :)
  12. westom

    westom Guest

    If the technicals were wrong, the poster would have challenged the
    facts. Those who cannot attack the messenger. IOW Adrian is
    declaring he does not have sufficient knowledge to disagree.

    A 250 watt Dell supply may be sold to the technically naive as a 360
    watts supply. Neither number is wrong. Others who also have this
    rumored 'underrated' supply aslo had no power problems. Only the
    naive would post without technical facts. And that is only when I
    start posting - the challenge the technically naive to demonstrate
    'why' they know. Adrian could not probably for good (under educated)
    reason - an insult he earned by replying without facts and numbers.
  13. ZACK`

    ZACK` Guest

    to test them i use a PC/SPS TESTER
    just plug the 20/24 pin connecter in and
    plug in the power, leds idicate health of
  14. westom

    westom Guest

    Tester can identify a defective supply. But it obviously cannot
    report a good supply. Ciritical to testing a supply are voltage
    numbers when supply is under maximum load. Tester can provide that
    load and provides no numbers.
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