Saipan Modulator Upgrade Project: February 1, 2007 (Day 18). Day 18 began with testing the water-cooling system for the RF power amplifier stage of the transmitter. With power applied to the pump the entire cooling system was checked for leaks. It was good to see water flowing again out of the power amplifier vacuum tube cooling jacket through the Pyrex glass and back into the water reservoir. Because the water flows through components that have 14,000 volts applied to them, the water has to be de-ionized to assure that it is highly resistive and does act like a current conductor.