Power Supply Introduction

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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)

CheckDesignationComponentMarkingCategoryOrientationNotesCircuit
C070.1 uF(smt) black stripe (smt) black stripeSMT 1206Power Supply
C090.1 uF(smt) black stripe (smt) black stripeSMT 1206Power Supply
U1LM78L05 voltage regulatorLM78L05 LM78L05TO-92Power Supply
D11N40031N4003 1N4003AxialPower Supply
C0610uF/16 VDC ElectrolyticPower Supply
C0810uF/16 VDC ElectrolyticPower Supply
ground leadshunt wire (cut-off lead)Cutoffconnect at /ENRXPower Supply

Power Supply Summary Build Notes

Power Supply Detailed Build Notes

Bottom of the Board

Power Supply Bottom View

Install SMT Caps

Two SMT capacitors are mounted on the bottom side of the board in the locations shown

CheckDesignationComponentMarkingCategoryOrientationNotes
C070.1 uF(smt) black stripe (smt) black stripeSMT 1206
C090.1 uF(smt) black stripe (smt) black stripeSMT 1206

Top of the Board

Power Supply Top View

Install Electrolytic Caps

Note that the positive lead on an electrolytic capacitor is the longer lead and goes into the hole marked +. The shorter, negative lead is on the side that has a grey band painted from the bottom to the top of the cylinder. Slightly spread the leads of the capacitor on the bottom side of the board to hold it in place and solder one lead. Check that the capacitor has been lightly snugged to the board and reheat the solder if necessary to adjust the position of the capacitor. Solder the second lead and cut both leads flush to the bottom of the board.

CheckDesignationComponentMarkingCategoryOrientationNotes
C0610uF/16 VDC Electrolytic
C0810uF/16 VDC Electrolytic

Install U1

U1 is a 5 volt regulator that will convert the 9-12 vdc input to a well-regulated voltage between 4.6 and 5.4 volts. Mount the U1 on the place provided, paying attention to the silk-screened pattern on the board.The three-hole patterns for mounting U1 are closely spaced and careful soldering is necessary to prevent solder bridges between leads and to make sure each lead is properly soldered.

CheckDesignationComponentMarkingCategoryOrientationNotes
U1LM78L05 voltage regulatorLM78L05 LM78L05TO-92
Take ESD precautions

Install D1

Mount diode D1 (1N4003) in hairpin fashion, with the anode end flush with the round, lower hole and the band (cathode) end bent into a hairpin inserted into the hole in the square pad. This provides a good measuring point to validate the voltage across C6.

CheckDesignationComponentMarkingCategoryOrientationNotes
D11N40031N4003 1N4003Axial

Install Ground Testpoint

Using a length of lead that you have cut off after mounting D1, fashion a loop to serve as a ground test point and solder it into the two holes at the lower left hand corner of the board, bridging the two holes.

Install Ground Testpoint photo
CheckDesignationComponentMarkingCategoryOrientationNotes
ground leadshunt wire (cut-off lead)Cutoff
connect at /ENRX

Power Supply Completed Stage

Top of the Board

View of Completed Top

Bottom of the Board

View of Completed Bottom

Power Supply Testing

Visual Inspection

Test Setup

Using very good lighting and magnification, carefully inspect the solder joints to identify bridges, cold joints, or poor contacts.

Current Draw (DMM)

Test Setup

Test for current draw in 2 ways:

  • In one test there is also a 1k resistor in the series "chain" as well.
  • in the second test, the setup is the same except that the current-liminting resistor is removed

Current draw test below uses a 9 Vdc battery for the power supply

Current Draw (DMM)

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
with limiting resistormA< 93.97_______
no limiting resistormA3 - 43.97_______

Voltages (DMM)

Test Setup

Measure the voltages with respect to ground at the testpoints indicated

Voltages (DMM)

Test Measurements

TestpointUnitsNominal ValueAuthor'sYours
+5V point (see above graphic)Vdc4.5 -5.54.92_______