If you open up task manager while your computer is running( control+alt+delete the click on task manager) and go to the 'Performance' tab, you can see from the memory bar chart how much of the RAM your machine is using. If you monitor this while doing normal tasks you will see if more RAM will speed your machine up. If while doing normal tasks your RAM is hitting or is near maximum frequently then more RAM will speed it up. If while doing normal tasks your RAM never reaches maximum, more RAM will not speed your machine up.
You could have damaged your digitiser cable during the repair. The digitiser cables are extremely fragile, and if they are damaged the your phone will not respond to touch. Try either using your screen on another 3GS, or a different screen on your 3GS. Also- No 6 Connector is Wifi Antenna No 7 is Wireless signal antenna Neither of these should cause the touch screen to be unresponsive, just bad wifi and GSM connection. Last thing to check, is that the phone has started up properly before you try an use the touch screen. My 3GS takes 30 secs - 1 min after booting before the phone has started up properly, and the touch screen works. Hope this helps. Michael
Error codes in the 2000 range are generally related to USB problems, make sure you're using a high powered USB port directly on your computer, no hubs, no keyboards. Make sure they only things plugged into your USB ports are your phone, keyboard & mouse...nothing else. Disable or uninstall all firewalls & anti-virus software. Source :https://discussions.apple.com/thread/261...
I am such a fool. I have eventually figured out that as I always charge my phone at night, that was the issue. The phone oddly does not respond well to being used while on charge. Maybe something to do with me using an unoriginal charger? Anyway, solution being, unplug while using!
When I changed my iPhone 4 screen I had to disconnect the battery. On reassembly I put the battery grounding clip in wrong ( a small black L shaped piece) and the iPhone did exactly as you described : black screen repeated charging noise. I may be that the battery is not connected properly. This may be different for iPhone 5, but it doesn't hurt to check. Hope this helps.