SoftRock Lite - Power Supply

Description

The power supply must be the first stage to be built since all subsequent stages will need power. And the power they will need is around 5 volts. This stage takes the voltage in, whether 12v as prescribed or 9v in our case and converts it to 5v using U1 the 5v voltage regulator. D1 provides reverse voltage protection.

Components - yellow on schematic

• U1 - LM78L05
• D1 - 1N4003
• C6 - 10uF +
• C7 - 0.1uF smt, bottom between D1 and C6
• C8 - 10uF +
• C9 - 0.1uF smt, bottom near + lead of C8
• C10 - 0.1uF smt, bottom near pin 16 of U4
• C15 - 0.1uF smt, bottom near pin 8 of U5
• 9v battery clip

Here is a view of the bottom of the board showing where the SMT caps are placed. Since there is no silk screening or board layout diagrams for the bottom of the board, this is important. On the left is C10, you can see the lead connecting it to pin 16 of U5, well that is U4. Toward the lower edge is C15 with a lead connecting it to pin 8 of U5. In the upper right hand corner is C7, between the pins for D1 and C6. Toward the center of the board is C9, near the + pin of C8.

Here you can see the four components that populate the top of the board for the power stage. They are the regulator, diode and two electrolytic caps in the upper left corner. The bare alligator clip is attached to the enable RX jumper. The covered alligator clip is attached to the v+ test point just below C13.

Test

I have soldered a jumper wire in the enable RX holes in the lower left corner of the board to be a ground point. For a v+ test point I have soldered a wire in a test hole located immediately below C13. Using you multimeter, measure the voltage between those two points. It should be just under 5v. Another check you can perform is to measure the voltage from exposed D1 lead and ground. It should be slightly below the voltage source because of the voltage drop through D1.

My measurements were as follows:

• Battery - 8.81v
• Diode - 8.13v
• Test Point - 4.91v