Power Supply Introduction


This stage supplies the "regular" 5 volt power rail, for powering the CMOS chips on the main part of the board.

Note: throughout these notes, they will refer to the board in terms of:

Unlkess otherwise noted, all photos/graphics of the board layout are displayed herein with the top edge UP.

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Power Supply Schematic

(Resistor testpoints (hairpin, top, or left-hand lead), as physically installed on the board, are marked in the schematic with red dots)

(Click for Full Schematic)
Power Supplyschematic

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Power Supply Bill of Materials

Stage Bill of Materials

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

168 1/6W 5%bl-gry-blk-gld bl-gry-blk-gld1/6W
11N40031N4003 1N4003Axial
24.7 uF 10% 16V X7R RAD475 475Ceramic
1shunt wire (cut-off lead)Cutoff
14 X #4-40 hdw (nut, bolt, washer, spacer) HDW
1DC Power Jack PCB Mount (rt-angle) Jack-RA
1Ensemble RX PCB (board)Main Board
1DC Power Plug 5.5/2.1mm Pos Ctr Plug
1LM78L05 voltage regulatorLM78L05 LM78L05TO-92

Power Supply Summary Build Notes

Power Supply Detailed Build Notes

Top of the Board

Power Supply Top View

Install Power Supply Components

Install the Diode with the lead on the cathode (banded) end forming a hairpin lead and the anode end snugged up against the board.

D31N40031N4003 1N4003Axial 
PCBEnsemble RX PCB (board)Main Board 
R1468 1/6W 5%bl-gry-blk-gld bl-gry-blk-gld1/6WS-N
U07LM78L05 voltage regulatorLM78L05 LM78L05TO-92 
C044.7 uF 10% 16V X7R RAD475 475Ceramichoriz
C054.7 uF 10% 16V X7R RAD475 475Ceramicvert
J03DC Power Jack PCB Mount (rt-angle) Jack-RA 
P1DC Power Plug 5.5/2.1mm Pos Ctr Plug 

Install /RX EN (Ground Point)

Use a good strong piece of wire, as this will be used as a ground connection point for a number of tests throughout the build.

Install /RX EN (Ground Point) photo
/QSD ENshunt wire (cut-off lead)Cutoff 
(use for regular GND connection point)
mtg_hdw4 X #4-40 hdw (nut, bolt, washer, spacer) HDW 
Can install later. four each of 3/8 inch 4-40 Phillips head screws,4-40 nuts, 1/8 inch long #4 nylon spacer and #4 nylon washer

Power Supply Completed Stage

Top of the Board

View of Completed Top

Power Supply Testing

Current Draw

Test Setup

Measure the resistance (after the input diode) on the power input to ensure there is no short circuit. Measurement can be taken from the hairpin of D3 and the "/QSD EN" ground wire and should read in the Megohm range.

If the measured input resistance is within reason, measure the current draw with your mA meter inserted in series into the positive power lead.

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
D3 hairpin lead (WRT GND - "/QSD EN")ohms> 1M7 M and rising_______
Current DrawmA< 84.3_______

Voltage Test

Test Setup

With 12 V dc applied to the board (author's gel cell was at 12.89 Vdc), measure the voltage after D3 and measure the output of U7 (the 5 Vdc rail)

Measurements are with respect to (WRT) the regular ground plane (i.e., the non-USB side) of the board.

Voltage Test

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
At Cathode of D3 (WRT regular ground)Vdc.6V less than input12.3_______
At hole for R27 hairpin lead (WRT regular ground)Vdc54.92_______