19-08-2024, 11:03 AM
Not even a relay, Gary.
The power supply contains a separate supply that is always present as long as the PSU is plugged in. This powers a small section of the motherboard that monitors the front panel switch. When pressed, it turns on the main power supply - it does that by shorting the green wire to ground using a transistor in some form, which in turn enables the controller IC in the main PSU to come out of standby.
Seems complicated, but it allows the computer to be turned off by the operating system once you've shut it down. Remember the days of waiting for the "It is now safe to turn off your computer" message, before pressing the mechanical mains switch that older machines had? Happy days! Funnily enough, my digital sound desk says exactly the same message once you've shut it down - I suspect it's a tribute to Windows 95/98.
In this case, it's definitely worth checking the switch - it's just a simple momentary type, so 2 wires back to the motherboard that should just unplug for ease of testing. If that seems OK, I would try a replacement PSU next. Sometimes the 5V standby supply gets tired, which is fair enough given that it's likely been running 24/7 since you built it.
The power supply contains a separate supply that is always present as long as the PSU is plugged in. This powers a small section of the motherboard that monitors the front panel switch. When pressed, it turns on the main power supply - it does that by shorting the green wire to ground using a transistor in some form, which in turn enables the controller IC in the main PSU to come out of standby.
Seems complicated, but it allows the computer to be turned off by the operating system once you've shut it down. Remember the days of waiting for the "It is now safe to turn off your computer" message, before pressing the mechanical mains switch that older machines had? Happy days! Funnily enough, my digital sound desk says exactly the same message once you've shut it down - I suspect it's a tribute to Windows 95/98.
In this case, it's definitely worth checking the switch - it's just a simple momentary type, so 2 wires back to the motherboard that should just unplug for ease of testing. If that seems OK, I would try a replacement PSU next. Sometimes the 5V standby supply gets tired, which is fair enough given that it's likely been running 24/7 since you built it.
