60W Transistored Power Amplifier Circuit

60W power amplifier circuit

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%.

Parts List

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

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