STEREO AMPLIFIER

INSTRUCTION SHEET

Price - Stock No 420

Price - Stock No 421 (100mm Speaker)

The TDA2822M  IC used in this project is a dual amplifier built  into an  eight pin chip.  It consists of two channels, each identical and with external  components  to  provide  a  very  simple  but  powerful  stereo amplifier,  with  a  gain  of  39dB and a current draw of 9mA with supply voltage in the range of 1.8 - 15 Volts.  It  will plug into the earphone socket of Walkman type machines and give excellent quality stereo sound from  two  speakers.  Students  are encouraged  to  research  the  fascinating  technology  of  speaker box design.

With 55 mm 0.25 Watt Speakers

With 100 mm 2 Watt Speakers

Check Your Kit

Schematic

Component Layout

Construction

1. To  make up the Kit, firstly check the PC Board for any damage. Check continuity of all tracks  with  a  multimeter  or  an  electronic circuit tester.
2. The two resistors can be bent to shape and fitted,  and  the  IC socket  pushed  into  place.    Solder  them  but be careful not to bridge across between the legs of the IC socket.  The best way to  solder  is  to heat  the  track  beside  the  leg  and apply a touch of solder.  When the   solder "takes" to the track add more solder and move the soldering iron to touch the leg.  Build a small cone of solder making sure you  have  heated the leg enough for the solder to take.
3. The two 0.1 uF capacitors (104) are not polarised so they can go in any way round.  All the other capacitors are electrolytic so  you  must observe the polarity of each.  Look on the body for an arrow pointing down one  leg.   This  leg is the Negative (K) leg of the capacitor.  Check the drawing for correct polarity, and push them into place.  Bend the legs  to stop them from falling out and solder.
4. The two trimpots can be matched to their holes, pushed into place and soldered.
5. Pins are provided to terminate the input and output wires.  Their holes are drilled larger.  Push them in and solder.
6. Find the small + and - markings on the speaker and solder lengths of  Fig.8 wire to them.  The wire with the black trace is usually used for  the  +ve  line.   The  -ve  wires from the speakers should be joined and soldered to the circuit board pin in the earth rail of the PCBoard.
7. Connect the 3 Core wire to each of the input pins and ground (common) on the PC  Board and  the  other ends to the two channel terminals of the stereo plug and common. 
8. To fix the battery holder in place first melt a dob of solder  to each leg up near the plastic, and also beside each of the two holes on the Board,  but  keep the holes clear.  Push the holder into place, right down  towards the Board.  Use the tip of the soldering iron to fuse  the  solder together.  There  is  also  a  switch to be connected across the +ve rail as the drawing shows.  Solder both wires to the one side of  the  switch,  centre and one end.
9. You will find that the legs of the IC are spread too wide to fit into the socket.  Place the four legs on one side of the IC on  the  table and  push gently so they are bent in slightly.  Repeat for the other side. Find the locating DOT on the top surface of the IC, turn it so it  is  the way the drawing shows and push it into its socket.

        Test  your  amplifier  by  plugging  into the earphone socket of your radio or player, turn the volume down, and switch on.  Adjust balance with the trimpots.  Mostly you will find that the Amp will work first time.

MORE INFORMATION

View the Datasheet for the TDA 2822.

TROUBLESHOOTING

Troubleshooting will consist of:

• check all components for values and location
• check all polarities
• resolder any or all joints
• make sure the battery holder is soldered to give contact

Contact CdS electronics

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