Finally got around to taking apart and fixing 30+ non working nes sytems i've had sitting in a box. I'm left with about 5 that I can not get to work.

All have the same issue. Lock out chips have been disabled, new pins but still get a soild grey screen.
Anyone else run into this problem and find a fix?

Yes what has happened is since the pins are new it causes issues reading the games until the pins have loosened. I have this same issue and when I wiggle games a little they fire right ip

Ya that doesnt seem to be the case. I can put them in a working machine and have no issues. When I try the same pins in the non working machines all I get is a grey screen

I did one of mine with new pins once. If yours is like mine and others, then you can't push the cart down anymore. Just push it in and don't click it downwards.

I boil mine now.

Not going to mess around with boiling as I have an ultra sonic cleaner. The pins are not the issue its somthing going on with the systems... I just cant seem to pin point the issue.

I did notice where the pins clip on the main board there some missing coating from the contacts. Seems all of the ones with issues have this same theme. I'll try and take a picture when I get home

I've noticed that sometimes the pins get bent easily on the new connectors. Make sure this didn't happen to you.