If you really don't want mains power at the
front panel at all, then a
relay
is paobably the best solution - lots of room to mount it (and the xfmr to
power it), and you don't have to modify the front panel.
Surely a transformer would need to be powered all the time?
So? DEC did that in their power controllers. I am quite sure you have
plenty of trnasformers powered all the time anyway -- the doorbell, the
clock/timer in the cooker/microwave oven, the VCR, ATX PSUs, etc.... OK,
some of those are SMPSUs running in standby mode, but the point is that
there's plenty of circuity energised all the time.
And don't you unplug your classic computers when you're not using them? I
certainly do.
Why not use a nicad to pull the relay in, and charge it up when the unit
is on? If the nicad was flat, you could just have an ordinary pushbutton
to bypass the relay to get you going.
Having had experience of NiCd powered power switches in machines like the
Torch XX and the Whitechapel MG1, I would not recomend this. NiCds always
seem to be discheargeed when you need them.
-tony