Valve Audio 802 Integrated not powering on :sd:

Hi Guys,

I bought this stunning piece of oom Schalk's engineering/workmanship secondhand around 3 years ago.
It worked flawlessly until I tried powering it up on Sunday afternoon.

As soon as I hit the power button, I hear feedback (hum) for about a second coming from the speakers before the unit shuts itself off.
Any idea what this could be?  Does oom Schalk's famous lifetime warranty apply to this legacy amplifier?

Thanks 
Theo