[Ron Ramirez]

Yes, assuming the wire is still protruding from the top of the tube envelope.

Remove the old solder, remove the cap. A good choice for re-cementing the grid (not plate) cap is Sauerisen cement. It is in powder form, and must be mixed with a small amount of water. Careful - a small amount of powder is all you will need. Additionally, it will stand up to the heat produced by some tubes and is therefore a great choice for re-cementing tube bases to the glass. (However, most tubes with grid caps normally produce little heat.)

Once the cement is applied inside the grid cap, reattach it to the tube, making sure the wire protrudes through the tiny hole at the top of the grid cap. Let the cement dry overnight, then re-solder the wire to the cap.