The Eimac 3CX4500F3/YU-108 is a medium-Mu, ceramic/metal power triode designed primarily for use in broadcast and industrial radio-frequency heating services. Its air-cooled external plate is rated for 6000 watts of dissipation. YC156 Conversion. This particular amplifier project started almost thirty years ago. Around 1973, the original chassis was modified to use a 4CX1000A. The YC156 triode is the third tube type to be used in this chassis. Why? Well, I was always unhappy with the 4CX1000A, and, I always wanted a tube with handles! This photo might show you why.