I've searched and have not found an answer to my problem.

D600 worked great as a back up / kids computer. The problem started when we got a chocolate lab puppy. She chewed thru the output side of two power supplies. I've tried a third power supply and batteries but I get nothing no lights.... I've tried holding the power button down for and extended time with the same results, nothing.

Can anyone provide any direction?

So you have removed all power(Battery and Power Adaptor), and held down the ON button for 30secs

And still when putting (say the battery back in) it's the same fault

Oh dear...

I would suggest to detach the HardDrive and Ram (reseat that is) and test again.
But the real concern is that something (the Mobo) has shorted somewhere, which may require you to dismantle the Laptop!

Yes, I have removed all power ( I checked and tried again). The HD is in the laptop I am working from now. Should I locate and remove the cmos battery?
I also reset the mem, same result, nothing. How do I test the MoBo?

No, anyway they're soldered in on laptops half the time.

It still could be Ram shot (faulty)
You basically need to swap parts (Ram; HardDrive; CPU <- Oh, this is inside now!)

Yes you need to dissasemble it
Then unplug the Display (from the Mobo) and test with an external Display
Then view the Motherboard for any "burn" marks
Possibly test with another CPU
And eventually BenchTesting (ie Mobo completely out !!!)
Until you have confirmed that the Mobo is gone.

Thanks!! I will get to it when I have a little more time. I have a duplicate box available so I should be able to mess around. I will provide my findings for anyone who searches in the future.

Thanks, here's hoping it's Ram
Don't reply if you've tried other Ram, Just wait until you try lots of other things too
It still could be simple, ie reconnect internal connections, who knows. Good luck

Tried everything I could must be the MB.