My mate had a hairline crack in his 3G LCD, so he ordered a new one from eBay (auction link) and got round to installing it.

Having hooked up the LCD to the frame and attaching all the ribbon cables, he closed up the phone, to find that there was nothing on display.

He cannot remember if he replaced the LCD with the phone powered up, I've read something that suggests doing so, requires a power cycle for the LCD to kick in?

That's all well and good but the home button and power button don't seem to do anything now?

Having heard this I advised him to bring it to me to take a look, I replaced my LCD without much of problem.

It looked fine, all the connections were good. I just couldn't understand it.

When he brought it to me the phone was powered up but nothing on screen, (as said, he cannot remember if he replaced the LCD whilst it was powered up) we knew the phone was on as we were able to mute/unmute/hear the phone ring.

I reconnected ribbons 1,2,3 and even 4, and closed it up again, still nothing.

I then tried just hooking the old LCD back up, to see if there was any play in that (all whilst powered on). Nothing, granted I only hooked up Ribbon 1 (presumably thats all that's needed?)

2 looks like the Digitizer, 3 looks like the earpiece speaker?

Again, like above, I've read something that suggests doing so, requires a power cycle for the LCD to kick in? Is this correct?

Is there any other explanation for this?

Do 2g LCD's fit? I'm just curious, but I've read somewhere else, that a 2g LCD might result in the symptoms we're having?