sony viao vgn tz37cn no post no display

Hi, I have a really old laptop sony viao vgn tz37cn that has a broken screen. I replaced the display by carefully checking the serial code and wearing an anti static wrist strap. Everything was fine but after I have done the replacement, I tried to boot up the machine, but there is no display, no hard drive movement. However, the fan is spinning, the power light is on. 

I turned off the machine, took off the memory wiped it and put it back, it was still not working. I tried to unplug the motherboard battery and put it back. Still didn't work. Anyone know what is going on out there? Thanks.