Power Supply Introduction


The purpose of this stage is to provide the 5 Volt power rail for the CMOS ICs (as well as provide for Power and TX LEDs and the 12 Volt input point. Make sure your external power supply has the correct volatge (12-13.8 Vdc) and it should be capable of producing 2 to 3 Amps. A faulty or underrated power supply is a very common problem.

See also the GenesisRadio On-Line Pictorials - Phase 1

This stage had two areas of the board which were populated to provide the 5 V power supply and the LEDs for RX and TX. In addition, there were some diodes that were populated throughout the board (1 zener and 21 regular diodes). Parts of this stage are spread across two of the schematics: "Genesis G** RX/TX PC Control + CW Monitor Design" and "Monoband HF SDR Transceiver Genesis G40".

Power Supply Schematic

Power Supplyschematic

Power Supply Bill of Materials

Stage Bill of Materials

(resistor images and color codes courtesy of WIlfried, DL5SWB's R-Color Code program)

22k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W  Power Supply
120 2W 1%red-blk-blk-gld-brn2W  Power Supply
211N41481N4148Axial  Power Supply
11N4734 5V6 Zener Diode1N4734Axial  Power Supply
4100 nF104 104ceramic  Power Supply
247 uH molded inductoryel-vio-blk-gld yel-vio-blk-gldchoke  Power Supply
4100 uF/25Vdc Electrolytic  Power Supply
1G40 Printed Circuit BoardG40  Power Supply
1green LED LED  Power Supply
1red LED LED  Power Supply
178L05 voltage regulator78L05 78L05TO-220  Power Supply

Power Supply Summary Build Notes

Power Supply Detailed Build Notes

Top of the Board

Power Supply Top View

Install Components for 5 V rail

Install all of the components, as per the graphic above.

Note: the LEDs are mounted such that their flat (cathode) side is facing toward the right-hand edge of the board (where the board is oriented such that the "WWW.GenesisRadio.com.au " label can be read normally at the bottom)..

B1G40 Printed Circuit BoardG40 
E138100 nF104 104ceramic 
E152100 nF104 104ceramic 
E3100 nF104 104ceramic 
E88100 nF104 104ceramic 
E111100 uF/25Vdc Electrolytic 
E28100 uF/25Vdc Electrolytic 
E39100 uF/25Vdc Electrolytic 
E4100 uF/25Vdc Electrolytic 
E178L05 voltage regulator78L05 78L05TO-220 
Take ESD precautions
L447 uH molded inductoryel-vio-blk-gld yel-vio-blk-gldchoke 
R1647 uH molded inductoryel-vio-blk-gld yel-vio-blk-gldchoke 
R28420 2W 1%red-blk-blk-gld-brn2W 
R732k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 
R742k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 
E298green LED LED 
E340red LED LED 

Install All Diodes to the PCB

The 21 diodes and their placement were, to borrow a phrase, "all over the board" - literally:

(All these 1N4148 diodes are not really a part of Power Supply unit. There is no functional reason to have them installed in this very first step. The reason is purely a practical one. to basically get rid of them as soon as possible while the PCB is not populated with taller components. Also due to the 'difficult to read' silk screen/print, it was thought that this would be an easy component to miss completely or to install incorrectly. Consequently, just grin and bear it!

Take great care to align the diode's black band with the corresponding band on the silkscreen.

Install All Diodes to the PCB photo

Install Zener Diode

Install the single zener diode as per graphic below. Again, this is not purely a Power Supply requirement, but rather a case of expediency.

Install Zener Diode photo
E2421N4734 5V6 Zener Diode1N4734Axial 

Power Supply Testing

Power Supply Test

Test Setup

Install temporary power leads at the points indicated in the graphic

  1. Measure the resistance on the power leads to be sure there is no short. You should see a very high (> 1MEGOhm) resistance
  2. Temporarily connect the power leads to a +12V to +14V power supply The green LED should light up.
  3. Measure the voltage on the 5V rail (pin 3 of LM7805) with respect to ground. You should see something on the order of 4.9-5.0 Vdc.

Note: the temporary 12V poweer leads will be used up through the end of phase 6 (original G40 project's Phase 4)

Power Supply Test

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
Power leadsMEGOhm> 11.9_______
Pin 3 (bottom pin) of Voltage RegulatorVdc55.02_______
Green LEDLitYesYes_______