My Dell D600 will not turn on?

Hi all,

Happy Christmas to all hope you're all having a good one.

My problem is that the above laptop does not power up?

I have tried the power supply on a meter at the connection end before plugging into the laptop and is reading 19.5v but when I connect the power connection to the laptop the power light on the power supply extinguishes and when I check the tester inside the laptop after the lead is plugged in the reading goes down to around 3v.

Has anyone this problem or know what may be wrong.

Thank you all for any help.

All the best.

Kindest of regards.

Rob.