This is the circuit diagram of 60W transistored power amplifier. This circuit was designed and built during the 80s. From then it works without problem. It does not present a particular construction problem, apart from the known: the attention to the supplied power source, choosing suitable heatsinks and good matching of the driver transistors. The diodes D3..5 should be placed on the heatsinks of power transistors to have thermal coupling with the output transistors.
With the trimmer R15, we regulate the voltage at the output of the amplifier [with long work hours and little heat stabilized]. With the trimmer TR1, we can adjust the bias current of the amplifier at 50 to 100 mA. The bias current can be measured if you measure the voltage drop at the ends of the resistors R36 and R37, for the voltage that are given in the circuit, the current is approximately 75 mA. The voltage indicated in above diagram can be different, but may have a tolerance of about +/- 10%.
|R1 = 1.8K ohm||R25 = 8.2K ohm||D1,D2 = 24V/1W Zener||C1 = 4.7uF/25V|
|R2 = 220K ohm||R26 = 27K ohm||D3….9 = 1N4002||C2 = 470pF|
|R3 = 27K ohm||R27 = 820 ohm||T1-2 = BC550C||C3-4 = 100uF/63V|
|R4,R10,R11,R17 = 3.3K ohm||R28 = 3.3K ohm||T3,T4 = BC560C||C5 = 68pF|
|R5,R9,R12,R16 = 100 ohm||R29 = 100 ohm||T5,T13 = BD530||C6,C10 = 330pF|
|R6 = 18K ohm||R31,R39 = 180 ohm||T6,T8 = BC414C||C7 = 22pF|
|R7,R13 = 3.9K ohm||R32,R38 = 6.8K ohm||?9 = BC416C||C8 = 220uF/16V|
|R14 = 10K ohm||R33,R34 = 1.2K ohm||T7,T10 = BD529||C9 = 100nF 100V|
|R15 = 22K ohm Trimmer||R35 = 82 ohm /1W||T11 = BD591||C11,C12 = 10pF|
|R18,R23 = 330 ohm||R36,R37 = 0.33 ohm / 5W||T14 = BD592||C13,R15 = 47uF/63V|
|R19,R21,R22 = 15K ohm||R40,R41 = 10 ohm / 2W||T12 = 2N5630||C16,R17 = 100nF/100V|
|R20 = 12K ohm||R42 = 180 ohm/5W||T15 = 2N6030||C18,R19 = 100nF/100V|
|R24,R30 = 82 ohm||TR1 = 4.7K ohm Trimmer|