short circuits SABER CARD, Instruction Manual

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1002
1002
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The green dot indicate a pin connected to
GND and the red dots indicate a pin con-
nected to Vcc. The closest GND and Vcc
pins are pin 15 and 16 of the CD4017 IC.
Polarity
Check all the components that are polarity
dependent. In this circuit, that would be the
LED’s and the ICs. The LED cathodes (faint
green mark on top of LED) should be con-
nected to the pad with a - symbol. If they are
connected the wrong way around, the LED
won’t work when the circuit is active. The
rest of the circuit should function though.
Make sure the ICs match the orientation in
the picture. Getting these wrong may be
fatal to the ICs.
Testing for faults
Before you power on the board, there are a
few things we need to do.
Visual Check
Firstly we need to do a visual check. We are
looking for solder bridges that connect two
pads that aren’t meant to be connected.
A magnifying glass is a good tool to have
when doing this.
If you see any solder bridges, bring your iron
up to temperature and drag it between the
two pads. You may have to repeat this a few
times. Make sure your iron is clean or the
solder won’t cling to it. Use flux if the solder
bridge isn’t parting.
Short Circuits
Now we need to check for short circuits (the
bad kind). If we have a short circuit some-
where on the board and we apply power,
you may destroy one of or both of the chips.
To check for shorts, get your multimeter and
put it in continuity mode ( ). Make sure
the black cable is plugged into the common
socket and the red cable into the red socket.
Touch the probes together and make sure
it makes a sound. Now press the black
probe on one of the GND contact (green
circle indicated in the diagram). Keep it held
there while you press the red probe onto the
Vcc(+) contact (the red circle indicated in the
diagram). Making sure they are both making
contact with metal, listen for a sound from
your multimeter. If there is none, excellent,
you don’t have a short between Vcc and
GND. You can jump over to the Power Test.
If you here a constant sound from your meter
when the probes are in contact with Vcc and
GND then you have a short. Check the IC
pins again for solder bridges. Focus on the
areas marked with boxes on the diagram.
Power Test
We can now connect the circuit to power.
Connect anything from 5-16V. The positive
lead/clip should be connected to the + pad
and the negative lead/clip should be con-
nected to the - pad.
If nothing happens, use a multimeter to
check the power supply. Check the IC ori-
entation again.
If one or a few LEDs don’t work, then check
their orientation.
Still having problems? Head over to the
forums on our website for help and sup-
port. www.shortcircuits.cc