Unplug the Deluxe Reverb from a wall socket. Discharging capacitance potential is strongly recommended for safe working conditions. Consult instructions on how to safely drain capacitors if you are not familiar with the procedure, because several hundred volts of electricity can be stored in the circuit.
Remove the four chassis mounting screws at the top of the amplifier, at each of the metal plates. Remove the cross piece on the back of the amp that guards the tubes. The chassis will slide out toward you, though frequently it will get caught on staples in the wood of the cabinet. You can exert force to overcome this resistance, but take care not to bend the faceplate of the chassis.
Locate the volume control for the vibrato channel once the backs of the potentiometers are exposed. It is approximately the middle of the chassis. On the back of the volume pot, a capacitor, usually orange in color, is soldered between two lugs on the pot. Clip one lead of the cap with side cutters, and tape off or shrink tube the exposed lead so it cannot contact the pot.
Use soldering equipment if you want to make a reversible modification. Remove one lead of the cap with a soldering iron, and tape or shrink-tube this lead as in the previous step. To reverse the modification, simply expose the lead, and re-solder it to its original location. Re-assemble your amp, and enjoy your new, warmer tone.