I've found many instructions on how to remove the valve assembly from standard Sankey 15.5 gallon kegs, but nothing for Heineken threaded kegs without the spiral retention ring. Miller Brewing has a very similar valve but there are some differences. I'll go into cutting off the top in another thread as the Heineken threads complicate things. I mostly followed Winemaker2's post about Miller kegs (see link for his post):
The first step is to relieve pressure, either tip the keg to the side and press the button, or drill a hole in the top. The valve can now be unthreaded, use a screwdriver and hammer on the tabs to turn it. A few taps should be enough to get it started and you can do the rest by hand.
One completely unthreaded you'll notice that the valve assembly still won't come out, there is an safety catch inside that prevents it from flying out. If you're coordinated enough you can depress the valve button while pulling it out. An easier way is to make a tool like below. It's 1 3/4" wide and 1/8" thick with a 3" bolt, a nut soldered to the bottom, and a hole in the middle of course. The main difference between the Heineken tool and the Miller tool is that the Heineken button is in the middle whereas the Miller ball is offset.
To use the tool, slip the flat steel under the tabs and make sure it's set well as there is going to be a fair amount of force on it. Screw in the bolt about 2" to disengage the safety catch. You can then withdraw the valve assembly by pulling on the bolt. You can also see the safety catch at the top in this image:
Here's the complete breakdown of the valve parts. I already cut the cage part off the top in preparation for keg top removal.
Thanks all! I've been having a great time reading all the posts over the last several months and finally found a way to contribute back to the collective