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Power Supply turn-on

By Spike6
Sep 26, 2006
  1. Hi: I am tired of the “soft shutdown” gimmick on all modern PCs. [If I wanted a Mac I’d buy a Mac!]. I'm now building a new PC and I’d like to get back to a single switch on an AC line outlet box where PC, Printer, VDU, etc. all come-on or go-off together without a need to push more buttons (like the old ATs). Can I accomplish this by simply shorting P/S plug pins 14 and 15 together permanently and ignoring the motherboard connected pushbutton or is there a downside to this seemingly simple solution?
     
  2. Rik

    Rik Banned Posts: 4,985

    Shorting those pins together long term can result in damage to the psu. I wouldnt recommend it.
     
  3. Spike6

    Spike6 TS Rookie Topic Starter

    Tks Rik:
    Is there an OK way to accomplish this? I'd like my ATX to behave like an AT -- that is to come up and boot automatically when AC power is applied.
     
  4. Rik

    Rik Banned Posts: 4,985

    The only way i can think of doing it would be to use a 555 timer to deliver a pulse to power up the mobo, but i have no idea how to go about it tho. The 555 timer produces a positive pulse so it would need to be converted into a negative pulse as shorting the green wire to a black pulls it down to ground.

    I have been experimenting with trying to get the 3v hdd led output up to 12v to run el string but i have the same problem, its easy to use a transistor to switch 12v using 3v as the trigger, however, the led output from the mobo is negatively switched too.
     
  5. Spike6

    Spike6 TS Rookie Topic Starter

    Ok then how 'bout this? Wire a sizable (maybe 100mfd @25v) capacitor across the PC start push button. When power is applied to the PC and the +5v standby power appears at the pushbutton the capacitor passes a brief pulse on to the mother board to signal it to start the PC. May need to wire a diode across the cap to discharge it when the power is removed if the back circuits don't do it.
     
  6. Spike6

    Spike6 TS Rookie Topic Starter

    It's in the BIOS!

    Hey, problem solved. Turns out there is a BIOS setting to accomplish this. It's called various things depending on the BIOS but it's usually something like "restart on power applied."
     
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