My best guess is a failing or under-sized power supply.
I've seen this happen when there's not enough power to spin up the 
drives properly. Rebooting seems to "warm them up" enough start.
Don't turn it off until you can replace the power supply.


[log in to unmask] wrote:
> On our homebuild ATX case the front panel ON switch has developed a 
> curious fault.
> 
> It switches the computer on, but then it hangs immediately with no POST or 
> screen signal.  All there is are the fans and front panel lights.
> 
> The procedure is to switch it off at the back of the case, on again, then 
> press the ON switch.  This always works, but it can take dozens of tries 
> before it eventually 'catches' and then boots up normally.
> 
> We've tried unplugging the CDROM drive because when it fails to boot this 
> drive light stays on, but it made no difference.
> 
> A hard reboot using the reset button also fails in the same way.
> 
> Hoping that this fault and its solution will be familiar to someone.
> 
> Thanks,
> 
> Neil Taylor
> 
>    

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