I have an iPhone 3GS to fix that will charge from the Apple charger but when plugged into a pc it won't charge and shows...

Well I have a iPhone 3GS to fix that I think is completely dead. When turned on it shows the screen informing you to...

Ok so I have an iPhone 3GS to fix. The backlight flashes on for a split second when I reboot then phone but apart from...

Well my other problem is fixed but I have run into a new one. After replacing the digitizer a strip of the lower section...

I would open it back up and check to make sure the LCD and digitizer connectors are connected properly and that the ribbon cables aren't damaged or folded between the mid plate and screen assembly. While it's open also inspect the mainboard connectors for damage.

I did manage to get it to charge fully with some fiddling and it held it's charge. I replaced the dock connector and now it charges 100% of the time and is correctly detected by the computer. Thank you for the help Turkey and Dan.

Judging by the look of the screen the first thing I would replace would be the LCD. If that doesn't work you may have fried the mainboard but I doubt it will come to that.

The first thing to try is a hard reset. You can do this by holding the home and power buttons in until you get the power off slider up the top of the screen. After it has shutdown power it on again and see if it has fixed it. If that fails then I would assume either the LCD or 6R8 coil is dead. Before you go ahead and replace anything I would first inspect the mainboard for corrosion and if you find any clean it with isopropyl alcohol. If after a clean it's still not working then I would first replace the LCD and if that fails then take it to a repair store to have the coil replaced. I hope this helps and best of luck with the repair.

There are multiple reasons why an iPhone won't turn on not just because the mainboard is dead. I'l start with some of the more basic fixes and hopefully one of the pros can expand on it. Make sure the phone is fully charged and powered on. Plug it into your PC and see if iTunes recognises it. If it doesn't it may be in DFU mode. Hold the power and home buttons for 10 seconds then release the power button while still holding the home button. If the phone is in DFU mode it should boot up. If you have previously opened it up check to make sure all connectors are seated properly and that everything is where it should be (e.g. grounding tabs/screws) That's a start at least. If you want proper help you will need to be more descriptive about the problem.