Back in 1959 after I had just upgraded to General, I threw together a modulator that used a 6AQ5 driver. The thing sounded crappy but I could modulate with it and the signal was readable enough that the other station could understand my callsign. Problem was, the 6AQ5 would overheat and after a couple of minutes would go into thermal run-away. The plate would turn red and the signal would become extremely distorted. It was built on a small chassis, so I turned it upside down and let the 6AQ5 poke down into a glass filled with water. That kept the tube cool long enough that I could make a complete transmission as long as it wasn't too lengthy.