Hi, [move]I am Gaark. [/move] [glow=red,2,300]Thank you [/glow] for your response about the variable psu.I read your discussion on the PSU only in the transistor/heating phenomena.If yo need to arrest more heating, one of the easiest way ( other than using any mechanical ) to simply control the AC input voltage to the transformer using a Traic by closed loop.If you adopt this the collector voltage cant reach more and the transistor is safe at any loading condition ( With in the limit of the source you have ) But i need formal calculation for a particular voltage / current output form the PSU.Before switching ON the PSU i need the predetermined setting. Please suggest me.Hope I get all sugestion from your side. Because i am a biginer in electronics. [glow=red,2,300]Waiting for your enthusiastic replays.[/glow]