Vaio boots up but no screen. Please help.

The DC jack for my vgn-cr42s broke so I bought a spare and soldered it to the existing wire. The laptop worked fine until I then dropped it and the replacement jack broke so I bought a replacement from another vaio that came with wire and connector/plug. After replacing this, the laptop turned on but there was no display. The CPU fan works, I can hear and feel the hard drive whirring, the DVD drive appears to read discs and the power and wireless LEDs are on. However, when I plug the keypad in and press caps/scroll lock etc the LEDs for these do not come on (May or may not be relevant).

I've read that the screen failing on these laptops is a common fault although I never had any problems until I  changed the second jack.

I would really appreciate any advice you can offer about what the problem may be, parts I may need or if I need take the laptop to a professional....

RIght, I've checked, double and triple checked and I really can't see any connections that havn't been made. I've taken both the RAM cards out, poered it up and there are no beeps. I've tried connecting an external display and there is no signal to it although it does come out of stand by for a split second when the connection is made.

RIght, I've checked, double and triple checked and I really can't see any connections that havn't been made. I've taken both the RAM cards out, poered it up and there are no beeps. I've tried connecting an external display and there is no signal to it although it does come out of stand by for a split second when the connection is made.

Also, when I turn it on, it is on for about 5 seconds, then turns itself off and straight back on again???

Hi, sorry for the delayed reply. I've reseated everything I can. I've never touched the CPU. Not sure where to go next...?

OK I will try re seating everything again but I just want to repeat that the laptop functioned as normal after the drop it was only when the battery drained completely and the machine turned off till i realised the jack had been damaged. and then after replacing the jack was when i got the problem of having no display...