I'm working on a 3 way switch in a stairway.  The house is old.  Knob a tube wiring.

The 3 way switch went bad at the bottom of the stair and I bought a new 3 way switch.  I found the hot wire and placed it on the single black screw.  I placed the other 2 wires, one on each side on the brass screws.

When I flip the switch the light comes on.  If I go to the top of the stairs and push the old switch button the light goes off.  Push the button again and the light comes on.

HOWEVER if the bottom switch is off the top switch does nothing. 

The only time the top switch works is if the bottom switch is on.  The bottom switch has power running to the single black screw. 

I can't figure this out.

I don't if this is the right place to post, maybe machinery would have been better but there are a lot of smart and talented people here so I'm giving this first chance.