Dual Side Power Supply

I recently ran up against a problem where I needed a dual sided power supply for an early 70s piece of equipment. The original manufacturer was out of business, and their PCB was encapsulated in potting solution. All I knew was the main board needed +18 and -18 volts, DC.

This board is based on the LM340/LM320 or 78xx/79xx series regulator. It can be constructed for +/-5, +/-6, +/-9, +/-12, +/-15, +/-18, or +/-24 volts DC.

As you can see it’s a very simple design using a few diodes, three capacitors, a regulator, resistor, LED, and two connectors for the transformer connection and DC out (if you choose to use connectors).

The project was designed with a slightly more expensive snap-in capacitor because I found this circuit to be very helpful not only in repairing the headphone amplifier, but also my relay switching panel for my amateur radio antenna system, a console project I have been working on, and a switching board that I’m using in our production trailer at work.

The circuit is very simple and I could have breadboard it, but I decided to make up PC boards so it looked professional inside equipment. After all, people judge you by results and the quality they perceive by looks, rather than how clever you can be by using a stryrofoam McDonalds hamburger box for the PCB. The corners are marked for supporting posts, which can be drilled out for (US) 4-40 or 6-32 threads.

This part list is for the dual 18 VOLT version. Modify as necessary for other voltages. The majority of the parts were found at Mouser Electronics, and can be ordered over the phone or via their web site.

Part List

Part Value     Device           Pkg      Description                                

C1   5,500 f   5985-35V5600     EB30D    Electrolytic Capacitors, Snap In. CDM
                                         Mfgr: Cornell Dubilier 381LX562M035K012

C2   5,500 f   5985-35V5600     EB30D    Electrolytic Capacitors, Snap In. CDM
                                         Mfgr: Cornell Dubilier 381LX562M035K012

C3   1 f       598-SEK010M050ST Radial   Electrolytic Capacitors, 1.0UF 50V
                                         Mfgr: Cornell Dubilier SEK010M050ST

C4   1 f       598-SEK010M050ST Radial   Electrolytic Capacitors, 1.0UF 50V
                                         Mfgr: Cornell Dubilier SEK010M050ST

D1   1N4005    512-1N4005       DO-41    Rectifiers 1.0a Rectifier
                                         Mfgr: Fairchild Semiconductor 1N4005

D2   1N4005    512-1N4005       DO-41    Rectifiers 1.0a Rectifier
                                         Mfgr: Fairchild Semiconductor 1N4005

D3   1N4005    512-1N4005       DO-41    Rectifiers 1.0a Rectifier
                                         Mfgr: Fairchild Semiconductor 1N4005

D4   1N4005    512-1N4005       DO-41    Rectifiers 1.0a Rectifier
                                         Mfgr: Fairchild Semiconductor 1N4005

D5   1N4005    512-1N4005       DO-41    Rectifiers 1.0a Rectifier
                                         Mfgr: Fairchild Semiconductor 1N4005

D6   1N4005    512-1N4005       DO-41    Rectifiers 1.0a Rectifier
                                         Mfgr: Fairchild Semiconductor 1N4005

D7   1N4005    512-1N4005       DO-41    Rectifiers 1.0a Rectifier
                                         Mfgr: Fairchild Semiconductor 1N4005

D8   1N4005    512-1N4005       DO-41    Rectifiers 1.0a Rectifier
                                         Mfgr: Fairchild Semiconductor 1N4005

IC1  7818      512-LM7818CT     TO220    Regulators, std pos, 18V, 1A, 4%
                                         Mfgr: Fairchild LM7818CT

IC2  7918      863-MC7918CTG    TO220    Regulators, std pos, 18V, 1A, 4%
                                         Mfgr: ON Semiconductor MC7918CTG

J1             571-6404523      .100     Flat Header 3P Straight Post tin 
                                         Mfgr: TE Conductivity 640452-3

J2             571-6404523      .100     Flat Header 3P Straight Post tin
                                         Mfgr: TE Conductivity 640452-3

LED1 4300H1LC  606-4300H1LC     T1-3/4   Through Hole RED
                                         Mfgr: Chicago Miniature 4300H1LC

LED2 4300H1LC  606-4300H1LC     T1-3/4   Through Hole RED
                                         Mfgr: Chicago Miniature 4300H1LC

R1   1.5k/8    270-1.5k-RC      Axial    Resistor, 1/8th watt, 1.5k            
                                         Mfgr: Xicon 270-1.5K-RC

R2   1.5k/8    270-1.5k-RC      Axial    Resistor, 1/8th watt, 1.5k 
                                         Mfgr: Xicon 270-1.5K-RC

--   66710ABPP 567-667-10ABPP   Htsink   Heat Sinks TO-220 w/pins  (qty 2)
                                         Mfgr: Wakefield 667-10ABPP

--   4-40x.5   608-R4-40X1/2    Hdwr     Screw, 4-40 1/2" stainless w/washer (qty 2)                           
                                         Mfgr: APM Hexseal R4-40X1/2

--   4-40      534-7248-3       Hdwr     Nut, 4-40 stainless  (qty 2)
                                         Mfgr: Keystone Electronics 7248-3

--   4-40      534-4700         Hdwr     Washer, 4-40, lock-offset   (qty 2)
                                         Mfgr: Keystone Electronics 4700

--   DPS1      DSP1             PCB      Single Side Printed Circuit Board
                                         Mfgr: RealOldiesRadio DPS1