Barrel type top spring valves
The credit for the article goes entirely to the members of the Trumpet Herald forum. Most of what follows is a direct quote from various people in a topic on that forum. Personally I never had the guts to experiment with the barrel, top spring valves of 1960's instruments without being able to see beforehand what the setup is. As far as I know, this type of top spring valve with the barrel was introduced in 1958 with serial number 800,000 and lasted through the end of the Elkhart period. It was used on the 6A/6B and 10A/10B Victor/Artist models, all the Connstellation cornets and trumpet (28A, 37A, 38A, 36B, 38B), the 8B Artist, probably the 60B and the 5A and 9A Victor models.
As they say, a picture is worth a thousand words:
To disassemble the valve, you need to remove the valve stem by turning it counterclockwise. As you are removing it, the valve stem will separate from the piston below the metal barrel.
If the threaded section and the valve-stem are stuck, a neat trick to dislodge same is to use one of those round rubber "jar-grip openers" (a thin piece of rubber, sometimes with adverstising imprinted upon it), combined with nylon-pliers. Nylon-pliers? Yes. These are usually yellow, found in hardware stores in the electrical-supply sections. They are used to grasp fuses from fuse panels, without conducting electricity accidently. They close shut with a rounded "jaw-section", about the diameter of a soda-bottle cap. They can also be used for stuck valve caps.
Be careful with this operation. If you unscrew the valve stems of this type of valve, you need to know that you have to re-install them very, very precisely, or the valves will scratch and get stuck! Also, you will need the exact correct replacement springs. If the springs are too small or too wide the valves will not work the same way. Those barrel-shaped valves from Conn are precison parts that need precision work. The tolerances (there is metal on metal - no nylon guides) are much closer than on Bach valves or other "modern" valve systems (just look at the amount of rotation and you can see what I mean). Perhaps it is better to go to a skilled repairman who knows about the needed precission for this kind of thing.