The output voltage increases linear with P1 and P3 adjust the current. P2 is used for adjusting the maximum output current (2A). This 50V power supply has a minimum output voltage arround 0.4V and maximum 45V. For 50V the main transformer is 42V / 2A, C5 = 4700uF / 80V, T4 = BF257, T6, T7 = BD245B . R12 has 470Ω / 5W.
If a short circuit appears the final transistor wont burn if are cooled enough.
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