Problem Solving with Half Split Method
Another method that has been around for quite some time is the half split method.
Sometimes it is referred as the half of a half method. I first heard about this many years
ago from a coworker of mine while I was working in a factory. He was a retired
electronics guy from the military. Essentially what the method does is allows one to
determine where a problem exists within the equipment.
So let us start with a common problem. You plug in your boombox into the wall to listen
to the radio. But the radio does nothing. What is your first reaction?
If you are like me your first thought is there is no power or the radio is broken. Yes those
are both real issue and will cause the problem from time to time but these are the most
extreme of measures. Using the half split, let us take the two extremes and find the
middle.
Fig J
Fig K
You plug in boombox and turn on the power switch. Do you see any thing that looks like
Fig L? No probably not. No flame or smoke. Oh a great FYI, the wiff test. Plug
something in for a few moments and then smell the item in question does it smell like a
component is hot? If so then there is an issue that needs further attention. Ok, so no
flames or loud pops or hisses, that is good do you see an indicator the boombox is getting
power, like the display or a big red light is on?
Fig L
Fig M
Fig N
Ok, for sticks and giggles at this point let us say that no the big red light is not on, there is
no display on the LCD and there is no smoke and fire to be found. The next step is to
take a half split again. We are going to focus our energy between the boombox and the
outlet. We should refine our extreme points from the on/off switch and the power outlet.
Fig O
Fig P
Take a multimeter and measure if there is a voltage coming from the end of the power
cord. This will be AC voltage so we will need to set meter to read AC. A note here
about common sense. The half split method is really just a means of steering us to the
correct location of the problem. Common sense should prevail no matter what method
you like to use to find a problem. If it were me instead of unplugging the cord and
measuring the voltage, I would have plugged in a lamp to that outlet or found somebody
willing to put there fingers in the outlet and see if it were life. Ah, ok maybe not the later
but you get my drift common sense.
So to make this as interesting as possible as you read this let us magically assume,
correctly, that there is electricity from the outlet. Half split from outlet to power on/off
button led us to measuring the voltage of the cord. Is there voltage? Does it vary as the
cord moves, are there frayed wires? Are the prongs on the connector bent or in some way
creating a loose connection to the boombox?
Everything checks out fine with the cord. Plug the cord back into the boombox and make
sure the power switch is set to on. Is there any indication that the boombox is on? No….
Time to half split again. The extreme points are from the power on/off switch to where
the cord comes into the boombox. We need to create a half way point to decide where to
focus attention at.
A logic point would be at the power supply. There sometimes, though not always, is a
fuse that is in place to protect the radio from voltage spikes.
Fig Q
Visual inspection of the fuse is only one step in determining if it is good. To properly
test the fuse it has to be removed from the circuit. The continuity needs to be checked on
it. That is the only way to truly know if it is good or bad. TRUST ME !!! I have seen
good looking fuses have a bad end on it. I got sloppy and did not verify continuity and
proceeded to try to find what was wrong.
Time for a side discussion. There is a Murphy’s Law that states the $2000 CPU will give
up its life to save the $0.39 fuse. It never seems to fail that all of the protection in the
world cannot stop all of the surges and problem issues. One thing that is clear is that the
fuse only protects against situations where more current is used than the circuit was
designed for. If a fuse is blown generally it means something in the circuit changed. The
load increased, a component failed, something is touching something else, whatever the
case the blown fuse only indicates that there has been a change. By replacing the fuse,
you have not solved anything. All that you have done is but the circuit back into service
with you standing over it.
Ok back to our half split activity. Let us assume that the fuse is good. The next step is to
inspect from the plug to switch. We measured the fuse and it is ok. That means we are at
a split again. From the fuse to the cord / plug. That means there has to be something that
is causing an issue in between these points. We flip over the circuit board and there it is a
black spot. It appears the magic smoke has been released from the circuit board. Once
the magic smoke has been let out it is impossible to get it all collected and stuffed back
in.
Fig R
The problem has been found
Half Split Activity
Consumer Electronics Activity
Objective: To use the half split method to find the problem.
Worth: 10 points
1. What do you think is wrong?
2. What are the start and end points you will initially use to mark initial observation.
3. What technique are you using to determine issue?
4. What is the next half of half location?
5. At this point was your initial solution probable or improbable to the cause?
6. STOP HAND OFF YOUR PROJECT TO ANOTHER GROUP
New group what do you think the initial problem is?
Does the previous groups half of half support your idea?
Where would you place your start and stop points at?
7. What environmental issues could have caused this problem?
8. Complete the half of half method. What was the problem?
9. What CAUSED the problem?
10. If there is more than one cause what do you surmise what caused what?