If they are flashing and then going out when you start it up, that's good. The 5101 chip is often the issue here. You said you replaced it with a nvram, do you have a 5101 you can put in the socket to test? I'd take a good look at your nvram socket and make sure no leads were damaged when desoldered. I'm sure you haven't done this but just in case....make sure the chip in in the right way....someone I know may have put a socket in backwards and then oriented the chip wrong because of it in the past
Have you tried the quick "off and on" that's listed in the guide? Basically once the game is on, (the led's have flashed and gone out) turn it off and back on quickly. If the game's attract lighting now comes on but not the displays, the issue is probably with the display driver. If not, I'd be back looking at the 5101/mvram chip.