Workaround needed for Mobo and ATX PSU .

By danone
Dec 6, 2005
  1. I am building a mediacenter computer with an Antec OvertureII case and Asrock 775Twins-HDTV mobo, but my surprise comes when i push the power on button, and nothing comes out. After a couple of tests, i realized that the problem is caused by the Antec psu,( with other psu the mobo starts ok, and this psu works ok with other mobo ,so.... I think that the motherboard checks the -5V signal, but the SP450 ATX v2.0 Antec PS does not have that voltage(there is only 19 pin in the 20 atx connector).

    Any ideas?.

  2. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    Pin 18 you mean? Or are we not talking about ATX?
  3. PanicX

    PanicX TechSpot Ambassador Posts: 669

    Um... if the connector is missing pins, then where is the confusion?
  4. mailpup

    mailpup TS Special Forces Posts: 6,964   +355

    Are you sure your motherboard needs that voltage? It's my understanding that - 5v is a nearly obsolete PC voltage and many newer power supplies no longer include it. That said, if yours does, I see no alternative but to replace the Antec with on that has - 5v.
  5. danone

    danone TS Rookie Topic Starter

    To mailup.
    Im not sure, but the point is that the mobo with that psu does not start (no video,beeps,nothing.Also if you press the power on button for 4 seconds or more, it does not stop.)
    With an nonbranded 450W PSU, the mobo starts fine. I am going crazy with that. The problem now is that the OvertureII case, has an special issue with the psu, the ac plug is in the same side of the dc outputs, So changing the psu is not possible.
    I was thinking to short the missing pin in the atx connector with gnd signal or -12v, but i need some advice before frying the mobo.
  6. mailpup

    mailpup TS Special Forces Posts: 6,964   +355

    I don't know but shorting it doesn't sound like a good idea. Different motherboard perhaps?
  7. Nodsu

    Nodsu TS Rookie Posts: 5,837   +6

    The proper way to do it would be to get a voltage regulator and use that to convert -12V to -5V. You should be able to pick up a MAX664 chip or something similar for ~$10 in your local electronics shop.
  8. danone

    danone TS Rookie Topic Starter

    Thanks everybody, but i give up. Still waiting answer from asrock (taiwan and european headquarters, but seems that's nobody home) so I am changing the mobo ( and the brand, of course!).
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