Dell Venue Pro 11 7139 will not power up

I was using my tablet a few evenings ago when it suddenly shut down without warning. Since then I have not been able to successfully start the machine.

It has been on charge with the white led showing overnight connected to the original charger with the original USB cable but when you press the power switch the led goes orange for 2 seconds then back to white.

I have taken the back off and removed the battery, held the power button in for 20 seconds as suggested elsewhere and after replacing the battery the machine did show the Dell Logo. Unfortunately it shut down straight away and I haven't been able to get any response since.

It appears that the battery is dead. Is there any way to test if it is being charged?

I am also concerned that the machine will not power up with the charger connected and the battery either in or out. Is this correct behaviour?

Any suggestions would be gratefully received as the machine is just out of warranty.

Thanks