I've had a memory daughtercard go bad on one of my Classics... thought the logic board was toast initially but swapped in another daughtercard with the same SIMMs (i cant remember how i diagnosed it but i think it was by accident) and it worled again. tried the removed card in the other classic (before the A/B went) and it didnt play ball either, with or without SIMM's installed.

But yes, that dark grey raster prior to bootup is normal... But it shouldnt stay there.