NES frustration

[CritAnime]

Replacing the 72 pin connector can sort it however you will find if your getting grey or garbled graphics it's probably crud on the carts. Best thing to do is buy a cleaning kit off the net that contains two solutions. One is white and removes the built up crud the second is a weak alcohol that removes the white stuff and any remaining crud. You will also need to a special bit to remove the screws in the cart case.
 
When openening the carts pay special attention to how the PCB fits in the plastic case. You need to make sure it goes back in the right way.
 
Also the new 72 pin connector can be tight when first used. It is reccomended to start with cleaned newer carts before using some of the older, launch titles. the older carts used a thicker pcb that could wreck the new 72 pin connector. It rare for it to happen but it's best to start with newer carts because the pcb is thinner and helps break in the 72 pin connector. Also don't leave carts in over night because undue stress on the connectors can cause damage over time.

[CritAnime]

the 50/50 solution doesn't work for all carts. Some carts have lots of corrosion on them that need almost polishing in order to get working. Trust me I spent weeks cleaning my bloody carts with 50/50 and then for some to do the exact same thing. I got a cleaning kit off the net and now even the ones that refused to work now work perfectly.
 
http://www.nintendorepairshop.com/products/78-1-Nintendo-NES-Total-Repair-Kit/
 
This is what I bought.

[CritAnime]

The 71 in one carts are usually pirate carts and only a hand full of games on it will be unique games. The rest might be rom hacks and name changes. Best sticking to normal carts rather than the pirate ones.

[CritAnime]

If it is the black bit then they are crap. I got a silver bit and it's still going strong 30 carts later. The trick is also to put a fair bit of pressure on the screwes, but obviously not enough tp break the cart this is to ensure that the bit has a good hold of it. I also made sure i set the electric screwdriver to it's lowest torque setting. However there are some older carts that have a weired screw to them. Kind of like a philips screw but smaller.