I have two projects about similar power supplies. They are internally regulated, adjustable between 2 to 13,5V. The output is symmetrical, that is, one is positive and the other is negative. Both can supply up to 1,25mA (give or take). I used one LM317 and one LM337 to regulate the output voltage. Also, to protect them from shorts, I had to add fuses (incredibly, the LM317 and LM337 are not shortable, unlike other regulators (althought it is refered in their respective datasheets that they are) - I tested myself with regulators from National Semicondutor).
The version 2 has some improvements relative to version 1, such as the LED's are driven by transistors, so their luminance will not vary very much. Also, in this version we have internal adjustable resistors, so the voltages can be locally fine tuned (mostly because of different room temperatures).
View attachment FADR0213V1A.pdf
List of components (version 1):
C1/3 6,8mF electrolytic capacitor (35V);
C2/4 1μF tantalum electr. capacitor (25V);
D1-4 1N5400 rectifier diode;
D5/7/8/10 1N4001 rectifier diode;
D6 Red LED (GaAsP/GaP);
D9 Green LED (GaP);
F1 630mA slow fuse;
F2/3 1,25A fast fuse;
IC1 LM317T voltage regulator (with 1,2°C/W heatsink);
IC2 LM337T voltage regulator (with 1,2°C/W heatsink);
Lp 230V~ resistorized neon bulb;
R1/12 71,5Ω metal film resistor (1% tol., 1/8W);
R2/13 42,2Ω metal film resistor (1% tol., 1/8W);
R3-7/14-18 115Ω metal film resistor (1% tol., 1/8W);
R8-10/19-21 28,7Ω metal film resistor (1% tol., 1/8W);
R11/22 680Ω carbon resistor (5% tol., 1/2W);
S1 DPST switch;
S2/4 6 position SP selector;
S3/5 4 position SP selector;
Tr Transformer 230V~ 2x15V~ 80VA.
View attachment FADR0213V1A(2).pdf
List of components (version 2):
C1/3 10mF electrolytic capacitor (35V);
C2/4 1μF tantalum electr. capacitor (25V);
D1-4 1N5400 rectifier diode;
D5 Red LED (GaAsP/GaP);
D6/7/9/10 1N4001 rectifier diode;
D8 Green LED (GaP);
F1 630mA slow fuse;
F2/3 1,25A fast fuse;
IC1 LM317T voltage regulator (with 1,2°C/W heatsink);
IC2 LM337T voltage regulator (with 1,2°C/W heatsink);
Lp 230V~ resistorized neon bulb;
Q1 2N3904 NPN transistor;
Q2 2N3906 PNP transistor;
R1/16 680Ω carbon resistor (5% tol., 2W);
R2/17 1,5KΩ carbon resistor (5% tol., 1W);
R3/18 95,3Ω metal film resistor (1% tol., 1/8W);
R4/6/19/21 20Ω preset resistor (5% tol., 1/8W);
R5/20 48,7Ω metal film resistor (1% tol., 1/8W);
R7-11/22-26 169Ω metal film resistor (1% tol., 1/8W);
R12-14/27-29 42,2Ω metal film resistor (1% tol., 1/8W);
R15/30 18KΩ carbon resistor (5% tol., 1/8W);
S1 DPST switch;
S2/4 6 position SP selector;
S3/5 4 position SP selector;
Tr Transformer 230V~ 2x15V~ 80VA.
The version 2 has some improvements relative to version 1, such as the LED's are driven by transistors, so their luminance will not vary very much. Also, in this version we have internal adjustable resistors, so the voltages can be locally fine tuned (mostly because of different room temperatures).
View attachment FADR0213V1A.pdf
List of components (version 1):
C1/3 6,8mF electrolytic capacitor (35V);
C2/4 1μF tantalum electr. capacitor (25V);
D1-4 1N5400 rectifier diode;
D5/7/8/10 1N4001 rectifier diode;
D6 Red LED (GaAsP/GaP);
D9 Green LED (GaP);
F1 630mA slow fuse;
F2/3 1,25A fast fuse;
IC1 LM317T voltage regulator (with 1,2°C/W heatsink);
IC2 LM337T voltage regulator (with 1,2°C/W heatsink);
Lp 230V~ resistorized neon bulb;
R1/12 71,5Ω metal film resistor (1% tol., 1/8W);
R2/13 42,2Ω metal film resistor (1% tol., 1/8W);
R3-7/14-18 115Ω metal film resistor (1% tol., 1/8W);
R8-10/19-21 28,7Ω metal film resistor (1% tol., 1/8W);
R11/22 680Ω carbon resistor (5% tol., 1/2W);
S1 DPST switch;
S2/4 6 position SP selector;
S3/5 4 position SP selector;
Tr Transformer 230V~ 2x15V~ 80VA.
View attachment FADR0213V1A(2).pdf
List of components (version 2):
C1/3 10mF electrolytic capacitor (35V);
C2/4 1μF tantalum electr. capacitor (25V);
D1-4 1N5400 rectifier diode;
D5 Red LED (GaAsP/GaP);
D6/7/9/10 1N4001 rectifier diode;
D8 Green LED (GaP);
F1 630mA slow fuse;
F2/3 1,25A fast fuse;
IC1 LM317T voltage regulator (with 1,2°C/W heatsink);
IC2 LM337T voltage regulator (with 1,2°C/W heatsink);
Lp 230V~ resistorized neon bulb;
Q1 2N3904 NPN transistor;
Q2 2N3906 PNP transistor;
R1/16 680Ω carbon resistor (5% tol., 2W);
R2/17 1,5KΩ carbon resistor (5% tol., 1W);
R3/18 95,3Ω metal film resistor (1% tol., 1/8W);
R4/6/19/21 20Ω preset resistor (5% tol., 1/8W);
R5/20 48,7Ω metal film resistor (1% tol., 1/8W);
R7-11/22-26 169Ω metal film resistor (1% tol., 1/8W);
R12-14/27-29 42,2Ω metal film resistor (1% tol., 1/8W);
R15/30 18KΩ carbon resistor (5% tol., 1/8W);
S1 DPST switch;
S2/4 6 position SP selector;
S3/5 4 position SP selector;
Tr Transformer 230V~ 2x15V~ 80VA.