Remember to isolate the 2N3055 transistors from the chassis/radiator! This is very important! Use a radiator (heat sink) of appropriate size and surface area; insulating and heat-conducting spacer or at least a thin mica; hot adhesive and thermal paste.
PSF14A20 Specs
- Heavy duty power supply 13.8 volt, 20 or 30 amps continue
- low ripple
- short-circuit protection
- HF-immunity
- Voltage can be set between 12,3 and +/- 15 volts
- only 0.35v drop at full load
- parts widely available and calculated way over the maximum load
PSF14A20 Parts (30 amp version PSF14A30 in blue)
- transformer capable of delivering 20 amps @ 15volt (30 amps)
- 4 x 2N3055 (6 x 2n3055) (you can also use the 2N3773 transistor)
Use a large radiator (heat sink) of appropriate size and surface area; insulating and heat-conducting spacer or at least a thin mica; hot adhesive and thermal paste. - IC 1: 7812 (small heatsink)
- D1: MB2504 is used as it is a 25 ampere rectifier bridge and should also be very good cooled.
Or you could use 3 times four BYW29 8 amp diodes (TO220 pinning, cooling). - D2 & D3: 1N4001 or simular
- D4: 1N5401 or simular (1N5400...1N5408)
- Zd: 15volt, 5watt (1N5352B) or a 15v 6 watt variant in the BZW03-Series
- C1: 47nF
- C2: 22000uF (+ 10000uF) 35volts
- C3: 100uF/35volt
- C4: 100nF
- C5: 4.7uF/35volt
- C6: 4.7uF/35volt
- C7: 100nF
- C8: 220nF
- C9: 220uF/25volt
- C10: 47nF
- C11, C12: 100nF
- R1: 2k2 / 1W
- R2: 10 1/2W (2,2 1/2W)
- R3: 6,8 1/2W (2,2 1/2W)
- R4': 1 Ohm 1/2W
- R5': 0.1 Ohm/5W
- R6: 2k2
- R7: 10
- R8: 2k2
- R9: 22
- R10: 1k5
- R11: 10
- R12: 220
- P1: 1k
- P2: 2k2 trimmer (to calibrate the meter that will be used to measure the amps)
- F1: 2A (3.18A)
- F2: 22A (35A)
Just to be sure to prevent HF entering through the mains use a ring core and turn the mains a few times around it (see insides pics).
Be sure to use thick braid wires!!! They need to handle 20 (30) amps continues!