Abstract: Some important technological problems with stable operation of the twoside electron beam pumped main amplifier used in the “Heavn1” high power KrF excimer laser system are described. They are the problems of the electric breakdown of the insulator support for water dielectric transmission lines, anode foil installation of large area electron beam diode, shape of Hibachi ribs that contact the pressure foil, and formation of diode post pulses and their damage to the anode foil and cathode emitter. Emphasis is put on the effect of different mainswitch breakdown times on diode post pulses and the determination of the optimal breakdown time.