Wiring for Power adapter?

Question

I have a 90w power adapter from an older notebook that will work with my HP DV5-1015nr. I transport my notebook between home and office. I'd like to utilize the older power brick, so that I won't need to transport a power brick back and forth. The tips on both adapters, of course, are of a different diameter.     
My multi-tester identifies that the tip is hot for both adapters. The problem I have is that the older power brick has two wires: core wire (+) and shield (-), and the newer power adapter has three wires: shield that is connected to the core of tip (+), black that is connected to outer part of cylindrical shaft that must be the ground, and white connected to inner part of cylindrical shaft (also negative?).
So do the black and white wires on the newer adapter need to be soldered to the shield on the older one?   

Answer 1

Usually when there are three wires and the plug has 3 pins to the outlet then,one is positive the other negative and the third is ground.
And my guess that the main concern to HP not providing the information on something as simple as a charger is so that they cannot end up beng held liable for either damage to the decice or person should Mr. Less Than Average Joe mess up the information and electrocute himself or case something to brst into flames Renault ng in a law suit. Case and point the lady who bought a coffee from McDonalds and promptly dumped it in her lap then sued for not being warned. She got $50,000 for that. Same things with choclate bar warnings about trace amounts of nuts, etc... so whereas I too get the frustration I understand their unwilingness to help.