How to build a cheap 3A regulated power supply

This is a design for a cheap high current power supply, with a small parts list.

=Specifications=
 * Voltage: 1.25-20V
 * Max Current: ~3A
 * varies depending on output voltage. Max current is larger than 2A and smaller than 4.5A, if proper transformer is used.
 * Internal current limit
 * Internal short circuit protection
 * Internal temperature compensation
 * Good Line regulation, load regulation, and ripple rejection

Problems

 * It does not go to zero, the lowest voltage is 1.25V
 * Current limit is different at different voltages.
 * At low voltages the IC limits the current. See Fig. 1
 * At high voltages the transformer limits the current, by saturating

=Components=
 * 1 - LM350 - 3 Amp adjustable Regulator
 * List of compatible replacements: LM150, LM150K, LM350, LM350A, LM350K
 * 1 - Bridge Rectifier
 * I used a RBV-1506 7.5A Bridge Rectifier, because i had one. You can use any Bridge Rectifier greater than 4.5A
 * List of compatible bridge rectifiers:
 * Or you can make one using 4 rectifiers rated greater than 3A
 * 2 - 1N4002 rectifier diode
 * List of compatible replacements: 1N4003, 1N4004


 * Capacitors
 * 2 - 1μF ceramic capacitor
 * 1 - 2200μF electrolytic capacitor
 * 1 - 1000μF electrolytic capacitor
 * Resistors
 * 1 - 220kΩ (optional with neon lamp, not needed if lamp has an internal resistor)
 * 1 - 220Ω
 * 1 - 2.5kΩ potentiometer


 * Large heat sink for the LM350 IC
 * Heat sink compound
 * Neon lamp
 * This is optional. Used to indicate power on.  If lamp has an internal resistor you do not need R1
 * SPST switch
 * Most single-pole single-throw (SPST) switches will work. Needs to handle 1A and 120V or greater
 * Transformer
 * 120V to 20V RMS
 * 50W recommended, if your get lower your current limit will be lower at higher voltages, due to transformer saturation

Components list

 * Components
 * R1: 220kΩ (optional with neon lamp, not needed if lamp has an internal resistor)
 * R2: 220Ω
 * R3: 2.5kΩ potentiometer


 * C1: 2200μF capacitor
 * C2: 1μF ceramic capacitor
 * C3: 10μF capacitor (optional)
 * C4: 1μF ceramic capacitor
 * C5: 1000μF capacitor


 * D1: 1N4002 rectifying diode (optional, protection)
 * D2: 1N4002 rectifying diode (optional, required if using C3)


 * T1: 1:6 transformer 50W
 * S1: SPST switch
 * NL1: neon lamp (optional)
 * U1: full-wave rectifier bridge
 * U2: LM350 voltage regulator


 * Hardware
 * Large heat sink
 * Box

=Schematic=

=References=
 * LM150 datasheet