Kitronik 2143 Manual

High Power (15W + 15W)
Stereo Amplifier
Build Instructions
Issue 1.0

High Power (15W+15W) Stereo Amplifier
www.kitronik.co.uk
Build Instructions
Before you put any components in the board or pick up
the soldering iron, just take a look at the Printed Circuit
Board (PCB). The components go in the side with the
writing on and the solder goes on the side with the tracks
and silver pads.
You will find it easiest to start with the small components
and work up to the taller larger ones. If you’ve not
soldered before get your soldering checked after you
have done the first few joints.
Step 1
Start with the three resistors (shown right):
The text on the PCB shows where R1, R2 & R3 go. Make sure that you put the
resistors in the right place.
R1 and R2 are 47K(yellow, purple, orange coloured bands).
R3 is a 1K(brown, black, red coloured bands).
Step 2
Solder the diode (shown left) into the board. When putting this into the board,
be sure to get it the right way around. The band on the diode must match up
with the band on the PCB. The diode is marked D1.
Step 3
Solder the PCB mount right angled on / off switch (shown right) into SW1 on the
PCB. The row of three pins that exit the back of the switch must be soldered,
but it doesn’t matter if you can’t solder the other two pins.
Step 4
There are three ceramic disc capacitors (as shown left). The 100nF capacitor
should be soldered into C2 on the PCB. This capacitor has the text 104 printed
on it. Then the two 220nF capacitors should be soldered into C3 and C5 on the
PCB.
Step 5
Solder the LED (as shown right) into the PCB where it is labeled LED1. When
putting it into the board make sure the flat edge on the LED matches the outline
on the PCB.

High Power (15W+15W) Stereo Amplifier
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Step 6
Now solder the two electrolytic capacitors (shown right). The capacitors have
text printed on the side that indicates their value. The 10uF capacitors should be
soldered into C4 on the PCB and the 470uF capacitor should be soldered into
C1. Make sure the capacitors are the correct way around. The capacitors have
a ‘-’ sign marked on them which should match the same sign on the PCB.
Step 7
There are three terminal blocks (shown left) that allow the power and speaker
wires to be attached to the PCB. These go into the PCB where it is labeled
‘POWER’, ‘OUT1’ and ‘OUT2’. Make sure they face towards the edge of the
PCB.
Step 8
Solder the dual potentiometer (shown right) into the PCB where it is labeled R4.
Make sure the volume knob is facing away from the PCB.
Step 9
The next step is to add the heatsink and amplifier IC (as shown left). The best
way to do this is in the following order.
1. Solder the heatsink to the PCB. The heatsink must be orientated so that is
matches the outline on the PCB. As the heatsink is a very large part it
may take longer than normal for it to be soldered. If you have a
temperature controlled soldering iron, turn it up to full just for the
heatsink.
2. Insert the amplifier IC into the PCB and attach it to the heatsink by using
the nut and bolt.
3. Solder the IC pins to the PCB.
Step 10
The kit is supplied with a metre of twin cable. This cable will be used to connect the two speakers. You
will need to cut this to the required length to connect each speaker in your enclosure design
(reserving a section for connecting the power jack later).
Take each piece of twin cable and strip the ends of the wire. Connect one end
of each wire to the two terminals on each speaker (as shown right). You will see
that the speakers have ‘+’ and ‘-’ indicators. At this stage it doesn’t matter which
way around, the wire is connected.
Take the cable connected to one speaker and connect it to the terminal block
labeled ‘OUT1’ on the PCB. The connections on the terminal blocks are also
labeled with a ‘+’ and ‘-’. The ‘+’ on the PCB needs to go to the ‘+’ on the
speaker and ‘-’ to ‘-’.
Repeat with the second speaker, this time connecting to the terminal block labeled ‘OUT2’.

High Power (15W+15W) Stereo Amplifier
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Step 11
The kit is supplied with a power connector (shown left) that can be mounted
into the side of a case designed to hold your amplifier. To connect this to the
amplifier board it needs a piece of cable (reserved earlier in step 10)
connecting to it. There are three connections on the connector. The middle /
rear connection should have one wire connected to it and the top
connector should have the other wire connected to it as shown in the
diagram.
Look at the diagram above and note which wire is positive / negative. They can be connected to the
terminal block labeled POWER ensuring the polarity of the wires matches the ‘+’ ‘-’ identifiers in the
PCB.
* If you would prefer, you can connect a power supply directly to the PCB without using the jack
connector. To do this first cut the barrel connector of the cable on the power supply. Then use a
multimeter to identify the positive and negative wires.
This is done by setting the meter to DC voltage and testing the wires with the power supply turned on.
If it gives a positive voltage the leads are the right way around. If the voltage is negative you need to
swap the probes around.
Once you know which wire is positive / negative they can be connected to the terminal block
labeled POWER ensuring the polarity of the wires matches the ‘+’ ‘-’ identifiers in the PCB.
Step 12
The stereo jack / iPod lead (see picture right) should be connected to the
‘INPUT’ terminal. First feed the wires through the strain relief hole. The black
wire should be connected to the terminal labeled ‘BLK’. The other two wires
can go to either of the two remaining inputs.
Checking Your Amplifier PCB
Carefully check the following before you connect the power:
Audio equipment may become damaged if connected to an incorrectly built amplifier.
Check the bottom of the board to ensure that:
All holes (except the 4 large (3 mm) holes in the corners) are filled with the lead of a component.
All these leads are soldered.
Pins next to each other are not soldered together.
Check the top of the board to ensure that:
The speakers, power lead & audio connections are connected to the right place.
The ‘-’ on the capacitors match the same marks on the PCB.
The colour bands on R3 are brown, black, red.
The silver band on D1 is next to the on / off switch.
The ‘Black’ labeled terminal on the ‘POWER’ connection goes to the centre pin on the DC jack.
The ‘Black’ labeled terminal on the ‘AUDIO’ connection has the black wire connected to it.
The flat edge on the LED matches the outline on the PCB.
Positive
Negative, shown
below other terminals

High Power (15W+15W) Stereo Amplifier
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Does the
LED light?
Yes
No
No
Fault finding flow chart Start
Connect power to the board and
set the switch to on.
Check
•The soldering on the DC power
socket for dry joints and that the
correct pins have been used.
•The connections are the correct
way around on the ‘POWER’
terminal block.
•The ‘POWER’ terminal for dry
joints.
•The LED is the correct way
around and for shorts / dry joints.
•The switch for dry joints.
•The diode is the right way
around.
Check
•R4 for dry joints.
Stop
Is any
music heard?
Yes
No
Is audio
coming out of
both channels?
Yes
Which output
doesn’t work?
Check
•R4 for dry joints.
•C3 for dry joints.
•IC1 pins 1, 2 & 4 for
dry joints.
•OUT1 for dry joints.
•The connections on
the speaker for dry
joints.
OUT1
Connect audio to the board
Yes, but one of the channels is
always at max volume and the
volume control has no affect
OUT2
Check
•R4 for dry joints.
•C5 for dry joints.
•IC1 pins 12, 14 & 15
for dry joints.
•OUT2 for dry joints.
•The connections on
the speaker for dry
joints.
Is there a ‘pop’
on power up?
No Check
•C4 for dry
joints.
Yes
Check
•R1 for dry joints.
•C4 for a short.
•Dry joints on IC1
pins 6, 7 & 9.

High Power (15W+15W) Stereo Amplifier
www.kitronik.co.uk
How the Amplifier Works
Power In
(20V max)
Speaker 1
C1
470F
Audio
Input
D1
C4
10F
C5
220nF
R2
47K
Speaker 2
TDA7297
Power switch
C2
100nF
R1
47K
LED
R3
1K
Out 1+
Out 1-
Out 2-
Out 2+
Vcc
Gnd
In 1
In 2-
Mute
Standby
C3
220nF
R4
Dual 10K Pot
The high power amplifier is a fairly simple circuit as all the hard work is done by the amplifier IC.
Working from left to right on the circuit diagram, the power comes into the board and goes through a
power switch. When the power switch is off this isolates power from the whole circuit. When the switch
is on, the LED will light. The brightness of the LED is set by the resistor R3. The capacitors C1 and C2 are
present to ensure that the power supply to the amplifier IC is stable. The diode D1 is included so that if
the power is connected to the board the wrong way around it shorts the power supply. The power
supply supplied with the kit instantly cuts the power. This is needed to protect the audio amplifier IC.
In the middle of the circuit is the audio input, this is divided down by the dual wipe potentiometer R4
which works as a volume control. The inputs are de-coupled into the amplifier IC through the
capacitors C3 & C5. In order to prevent noise on power up the resistors R1, R2 and the capacitor C4
keep the mute and standby pins in a low state until the power supply has stabilised. The amplifier
amplifies both the voltage and the current of the input and this is then driven into the two speakers.