New mosfets for the dual band amplifier

Four IRFP360 mosfets mounted on heatsinks inside the dual band amplifier

In March I bought new mosfets for the dual band amplifier ( see post 6 December 2015), but only recently had the time to fit them. I always knew that the original IRF640 types were underrated when I started running the amplifier from a 54V power supply, and there were reliability issues with several of them failing with a loud bang. The new type I've now fitted is the IRFP360 which is a 400V mosfet. During the last couple of evenings I've been transmitting with the amplifier for long periods without any further mishaps occurring. I had to fit these mosfets with a different orientation from the IRF640 ( see previous amplifier images ) as the mounting hole is insulated ( no insulating collar required for the bolt ) and the drain connection was made to the centre pin, not the case. A mica insulator, however, was still necessary under each mosfet between it and the heatsink. The insulator required is slightly larger than the standard TO-220 size. To begin with I didn't have any suitable until I found that Farnell stock them, ( item code 520-214 ). The mosfet and data sheet can also be found at Farnell, ( item code 864-9359 ).