OT: PC Power Supply

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the_constructor wrote:

If the replacement is a quality make and model and the original was a cheap "no name" - then the money was well-spent.
However, there is a mobo setting which determines how the machine responds to a power fail. I suspect that yours has been set (changed?) to reboot automatically on power restore. Hence it will boot whenever power is applied. The solution is to change the setting.
-- Sue
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I can't recall the exact details (like pinouts) right now but the ATX power connector carries +5V, maintained 5V and a "power up" line. The maintained 5V is used on the mother board to power circuitry which can switch the power supply on (not just the power switch but also LAN etc). IIRC it signals to the PSU by connecting the "power up" (or whatever it's formally called) line to 0V. It could easily be that the line is shorted to a 0V pin. The ATX pinout is available on line. Google.
Alternatively there are a few BIOS setting which alter power up behaviour. Have you been playing with them?
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wrote:

Check the BIOS settings. Many allow you to configure what happens when power is first applied - turn on, remain off, or revert to last-known state.

Easy way to check - let the machine boot and initiate a shut down. If it stays turned off then it's almost certainly not a PSU-related 'triggering' issue.
Mathew
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