Hi,

Something is shorting out the power supply.

When you turn the power on, you should see three colored LEDs on the internal power board (Yellow, Red, and Blue) - are they all illuminated?

Without the unit in front of me, it is hard to diagnose any further but I would suspect that a capacitor has failed on the internal power board.

You could remove the power to the drive (that plugs into the bottom of the internal power board) and see if that improves anything (just in case the drive has electronically failed), otherwise remove all the cards apart from the CO00 card and see if the unit powers up.
If it powers up OK (with errors as cards are missing), add each card in turn (with the power off), power up the unit, and see which card is causing the problem.

If you need any specific advice, drop me a PM.

Cheers,

Steve

Main: 861v6 (LPS), 808v6, UHD722, DSP8000SE Anniversaries, DSP5200.2HC, DSP7200.2, SW1600, Sky Q, Cambridge Audio BD, Roon, M80
Office: 861v4 (LPS), 818v3, 800v4, HD621, M&K S150P, DSP5500HC, M&K MPS2810 sub x2
Son's system: 861v4, HD621, DSP6000.2, DSP5200HC, DSP33
Spare: MCD, 100 Series, 200 Series, 500 Series, F80s, C15s.