For a long time I was going to share with you the materials on assembling a transistor amplifier with unipolar power, assembled in retro-topology, which is still of interest to some radio amateurs. At the forum Diyaudio this ULF...Electronics Projects, 2N3773 2SC5200 Amplifier Circuit 150W "audio amplifier circuits, transistor amplifier, " Date 2019/08/04
For a long time I was going to share with you the materials on assembling a transistor amplifier with unipolar power, assembled in retro-topology, which is still of interest to some radio amateurs. At the forum Diyaudio this ULF can be found under the name APEXAX6. This circuit does not need DC Protect, because the output of the amplifier is connected to the acoustics via an electrolytic capacitor. The recommended voltage of the secondary winding of the 35V AC transformer, at which the output of the power supply unit will be about 50V DC, the maximum permissible 60V DC. At a supply voltage of 50V DC, the amplifier delivers 35W of power to the load.
Output transistors 2N3773 can be replaced by 2N3055 with power supply up to 60V. In this version of the watering can, as I understand it, compared to the original circuit, instead of the 12k resistor, a multi-turn TrimPot 22k is installed, and instead of the 27R, which is in series with the diodes 1N4148, TrimPot 50R is installed to correct the quiescent current of the output stage transistors.
The diameter of the output capacitor on the PCB is 25 mm, you can put 2200mF / 63V, 4700mF / 63V or 6800mF / 50V.
150W Amplifier Circuit Schematic
Bias 20-50mA can be installed with 50R Pot, if the desired BIAS is not installed or you want to increase the quiescent current – increase the nominal value of the trimmer up to 100R … 220R, but you need to use sufficiently large radiators.
The power capacitor can be from 2200mF-63V. As a rectifier, a double ultrafast diode BYV34 is used in the TO-220 package, it is possible to put BYV32 or BYV36. On this board, the input electrolyte 1mF-63V is replaced by 1mF film nonpolar, and a power fuse is added. There are no trim multiturn resistors on the board, because the board author did not want to use them for this circuit. The diodes 1N4148 in versions 1.5 and 1.6 are in thermal contact with the output transistor heatsink, that is, they are pressed against it using thermal paste. The recommended transformer is 2x36V AC 75W for MONO or 150W for STEREO.
In this 2SC5200 version of the board instead of diodes 1N4148 added transistor MJE340, which is installed on the radiator along with the output transistors. For all transistors installed on the radiator, do not forget the insulating pads and thermal grease.
In the near future I will try to share with you the circuit and board of the stabilized regulated power supply, which the author recommends using for the APEX AX6 amplifier, the board of which does not have a rectifying superfast diode and a smoothing capacitor for power.
pcb drawing was made with Sprint-Layout free viewer; https://www.electronic-software-shop.com/lng/en/support/free-viewer-software/