Power Supply Schematic

Power Supply Schematic:

This funny power supply creates 5 volts for the CPU and digital logic and +/- 5.7 volts for the Analog input circuitry. It also provides a signal that indicates when the power has failed, so that the 8051 can enter its power-down mode and protect the user's configuration is the 8051's internal SRAM.

Several component values are unmarked. The capacitor after the bridge rectifier should be a large value, such as 1000 µF (larger values are ok or multiple smaller capacitors may be connected in parallel). It should be rated for at least 25 volts. The small capacitor attached to pin 2 of the comparator should be 0.1 µF. The comparator is a LM311. The eight diodes are general purpose rectifiers, so 1N4007 or similar diodes may be used. The zener diode is 5.6 volts. The 7905 voltage regulator must be attached to a heatsink.

• Main CPU Section Schematic
• Simplified Analog Input Schematic
• Complete Analog Input Schematic
• MIDI Port Schematic
• Front Panel Schematic
• Wiring Schematic - not on-line yet