Power Supply Introduction


This phase provides the power bus for the G3020, via the (temporary) 12V feed and the regulated 5volt output for the Integrated Circuits.

It provides the 5 Volt power rail for the CMOS ICs (as well as provide for Power and TX LEDs and ttemporary 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.

(go directly to build notes)

Power Supply Schematic

Power Supplyschematic

(go directly to build notes)

Power Supply Bill of Materials

Stage Bill of Materials

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

11 k 1/4W 1%br-blk-blk-br-br br-blk-blk-br-br1/4W
22k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W
120 2W 5%red-blk-blk-gld red-blk-blk-gld2W
11N41481N4148 1N4148Axial
5100 nF104 104Ceramic
147 uH molded inductor 10%yel-vio-blk-slv yel-vio-blk-slvChoke
1shunt wire (cut-off lead)Cutoff
2100 uF/25Vdc Electrolytic
1G3020 Printed Circuit BoardG3020
1misc hookup wireHookup
1green LED LED
1red LED LED
178L05 voltage regulator78L05 78L05TO-220

Power Supply Summary Build Notes

Power Supply Detailed Build Notes

Top of the Board

Power Supply Top View

Install Diodes

Take care orienting the LEDs (the flat side of both LEDs is to the board's Outside edge).

Be sure to mount the 1N4148 signal diode with the band facing in the direction of the voltage regulator, as indicated on the silkscreen.


D1-11N41481N4148 1N4148Axial 
D1-2green LED LED 
D1-3red LED LED 

Install Resistors and Capacitors

C1-1100 nF104 104Ceramic 
C1-2100 nF104 104Ceramic 
C1-3100 nF104 104Ceramic 
C1-4100 nF104 104Ceramic 
C1-5100 nF104 104Ceramic 
R1-420 2W 5%red-blk-blk-gld red-blk-blk-gld2W 
R1-11 k 1/4W 1%br-blk-blk-br-br br-blk-blk-br-br1/4W 
R1-22k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 
R1-32k2 1/4W 1% (2.2K)red-red-blk-brn-brn red-red-blk-brn-brn1/4W 

Install Voltage Regulator and Electrolytics

Take care to orient the electrolytic capacitors so that their "+" lead (normally the longer lead) goes into the hole marked "+". The negative lead is normally the shorter lead and there is usually a grey band down the side of the capacitor to designate this negative lead. Failure to orient the electrolytic capacitors so as to respect proper polarization can lead to an unanticipated fireworks display!

The LM7805 5 Vdc voltage regulator must be installed such that the flat tab at the backside of the regulator can lay down to and be flush with the board per the silkscreen layout. This requires bending the leads to approximately a 90 degree angle and then fastening the tab (heatsink) to the board with a nut and bolt.

Careful: Don't make this mistake and install the regulator backwards:

LM7805 installed backwards

U1-178L05 voltage regulator78L05 78L05TO-220 
Take ESD precautions
C1-6100 uF/25Vdc Electrolytic 
C1-7100 uF/25Vdc Electrolytic 

Install Choke, and Jumper

The 47 uH choke resembles a resistor but is a little shorter. There are 7 of these 47 uH (micro) in the kit, plus one 470 nH (nano).

JMP1-1shunt wire (cut-off lead)Cutoff 
L1-147 uH molded inductor 10%yel-vio-blk-slv yel-vio-blk-slvChoke 

Install Temporary Power Leads

Connect leads to the points shown above for 13.8 Vdc power supply.

PWR1-1misc hookup wireHookup 

Inspect the Completed Stage

Check to make certain the voltage regulator, the electrolytic capacitors, and the 1N4148 diode are oriented correctly.

Maske sure the jumper was installed in the space just below the voltage regulator.

Inspect the Completed Stage photo

Power Supply Testing

Voltage Test

Test Setup

Test the voltage regulator for +5 Vdc (start out using a 100 ohm current-limiting resistor in series with the positive power lead - just to make sure there are no shorts.)

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
The jumper just below the pins on the voltage regulatorVdc+5tbd_______