Ding ding ding!

It would appear that the remote turn on relay is the culprit. Looked and measured behind the sled - all power OK, including with the player in the sled. So measured the amp remote line and got continuity to ground...
Disconnected it from the amp - and player boots...

And I just realised I forgot to check that the remote out on the player has survived, something for tomorrow...

So, good thing is it pushes me to finally get the thumb out and do the upgrade to the DLS A7 that's been gathering dust on the shelf for way too long.
Bad thing - just this little digging around in the car ground me down quick... looks like I'll be looking for a shop to do the replacement. Hopefully someone is willing to install something they didn't sell.