In article ,
Charlie Pridham wrote:

If you have replaced the hard drive, motherboard and processor,
then the power supply is by far the most likely scenario. The
trouble is that the symptoms can arise from almost anything,
including peripheral boards if you have them, because of the way
modern boot software is written.

I do have a graphics card, so If the power supply replacement doesn't
sort it I suspect I can run without it as the main board appears to have
a connection for the monitor cable.

Could something like a card reader connected to the USB on the board
also cause it (I have one but no longer need it so it could be removed)

Yes. It's a little late now, but generally the first step (before
replacing anything) is to disconnect ALL optional peripheral boards
and peripherals, and see if it works. If so, add them back one by
one until it fails. If not, then it's the core system.


Regards,
Nick Maclaren.