Black screen on a 4000 usually means no CPU found, or the bottom of the motherboard is shorting out on the case. At least that's what I've come to learn -- it's handy having a pile of accelerators here to test units with.
If you don't have a 4000cr motherboard with the 030 already on it, I'd try booting it with a plain old 030 accelerator board installed to see if it works. That way you could at least eliminate the 040 board as the issue.
If you don't have one, I have around 40 of the things in a box here (all tested and working) and could send you one for cheap. If you're interested the cost to ship it to Norway by small packet is (US) $5 surface (up to 4 weeks) or $8.50 air (usually there in under 2 weeks). I have no clue what one of these boards would be worth, make an offer or maybe pick one up off eBay from me or somebody else.
Failing that, Amiga France (amiga.fr) has repaired A4000 motherboards for me in the past, they're reliable and do really nice work (most times you can't even tell which parts they've replaced unless you check with a magnifying glass). You might want to send your motherboard to them. On average it's been 100E to fix an A4000 motherboard through them.
