Hey guys! How are you? In this video we're going to learn
how to inject voltage to find a short circuit in lines
Hey guys, how are you? Edgar here one more time greeting you all from Yo Reparo
welcome to this new video
today we are going to take a little break from the lessons, but I am bringing
a contribution that is probably already well known to many people
but I still see people who struggle
to know of how to inject a voltage
A simple contribution, taking advantage of the fact that I have here
a phone in short circuit on a main line
remember that we have already seen
the main lines in the previous lesson
so we already know what I'm talking about
so, let's check this phone
look what happens to this phone
if I connect the iPower to this phone
which is the Power Supply
now it is off
but
when I connect it, look what happens with the Power Supply
the iPower is off
if I turn it on
the phone shows a short
of 700mA
that means there's a consumption/ a short circuit in a main line
this is an iPhone 7 Plus
we've already seen
there are 3 main lines, among them there are
the battery line, called PP_VBATT
there's VDD_MAIN
and VDD_BOOST
if we go to the ZXW I can explain it better
The three main lines right? First we have
the positive of the battery
this, this powers many circuits
passes through a Tigris and a Mosfet
after Mosfet which is in series
VDD_MAIN is generated
it could be any of those in color red and blue
any of those can be in short circuit
then it reaches a Boost
and from this Boost
it will turn into another main line called
VDD_BOOST
Ok then
if we could draw this
Imagine that we have a battery here, this is positive
and this is negative
what happens? The battery
reaches a connector
Ok
reaches a battery connector
and from the battery connector a line called V_BATT is generated
which is the battery voltage, 3.8 volts
after this it passes through a Tigris and Mosfet
and the output becomes
VDD_MAIN
Right? But then
this one reaches a Boost
and now it's called VDD_BOOST
Ok these are the three main lines, we have
then
PP_VBATT
VDD_MAIN
and VDD_BOOST
so now we have to
find which of these lines are shorted or leaking
"Edgar, how do we find short circuits?" With continuity
"Edgar, how do we find the leaks?" With diode mode
Remember that we can now measure the ohm of the line
So
Let's move to the microscope, and switch out multimeter to
continuity and let's check
first of all, let's see the ZXW
first I want to check the first line, the battery
I can check here
on the positive pin of the battery and see if it is shorted
if we go to the microscope
here
and check
it's not shorted
Now I'm going to check
VDD_MAIN
it passes through Tigris
Tigris passes to the other side and now it's called
VDD_MAIN
any of these capacitors should beep if it is this line
let's touch this visible capacitor from here
let's move to the microscope
it should be this capacitor
if we touch this capacitor
ok, it's not shorted
now we have learned that
this reaches a circuit called Boost
and now
it's called VDD_BOOST, so let's touch this capacitor from here
now if I touch this capacitor from here
look
we've found our shorted line
Now, what are we going to do?
I want to explain something before we continue
so we understand that not everything that heats is the problem
I'm going to move here
and now I will take any compressed air
any of these
that you use for cleaning
just flip it
and now you have a freezer
I'm going to freeze the board
now it's frozen
let's move to the microscope
and look what happens
let's turn it on
look, this from here heats up
Did you see it?
let's freeze it again
and again let's turn it on
look, this one heats up, "but Edgar why does that one heats up if it's not the problem?"
let's
do a little
drawing here
let's do a drawing here
Let's imagine that
here we have the battery
positive negative
reaches a connector
from the connector
now
it generates a line called PP_VBATT
Okay
What's the voltage of the battery? 3.8 volts
So, this
powers, for example, 2ICs
okay, 2ICs
among them, a capacitor here
this goes and reaches a
circuit called Tigris
and here's Mosfet
Okay
when these two get powered
another line comes out and is called
VDD_MAIN
Correct?
this has, to say something
70 components
among them, circuits, capacitors, etc
the line goes on and on
powers many circuits
and powers a Boost
from here
and in its output
now it's called VDD_BOOST
Correct?
So this powers, say, 10 components
and among them, there are some capacitors
between those 10 components feed some capacitors here
let's say this little bastard from here said "Today I don't want to work, I'm going to join together"
remember that a capacitor
consists of two layers
and this capacitor goes to ground
so, the layers were joined together
So what's happening? Why do we have
a short and why this Boost
is heating up?
Because, my battery from here
for example
it has 2900mA
so here
is someone who's telling
"HEY!"
"Give me more current!"
the current will always look for a way to go to ground, it will go to ground
no matter what
By the way, look at the cap I got as a present
with a little cup of coffee and my name on it
So
What's happening?
The capacitor is demanding more current
so what happen
with the current we have here?
It turns out that
the current travels from here, powers these
power everything, and keep going
let's make this thinner
powers Tigris and keep going
powers these 70 components
capacitors and all
and because here's someone who's demanding more current, more current is passing through
there's more current, so what's going to happen to this circuit?
It will heat up, because probably a current of this magnitude should pass and now it is passing this
this is happening because here's someone who's
shorted
this over here, so
What's happening? We've already touched continuity on battery, it didn't beep
VDD_MAIN, didn't beep
VDD_BOOST, it beeped
So, what's going on?
let's make an example, we have a line like this
and this line has
components
has ICs
has capacitors
has some more capacitors
and here more ICs, and the line continues
keep going and
and feeds more things
So, what do we have to do? We have already identified the line
I'll grab the tips
of my multimeter
and connect them to the Power Supply
positive and negative
Ok then, we found a short
a total short, it beeps to ground
but many times it could be a leak
"Edgar, what is a leak like?"
I grab a functional motherboard
and measure, for example, this line
let's say this line is 0.350
but I touched a bad line and it had 0.100
this is leaking out, any of these are letting go
some current, so, some of these are leaking out
We do the same, grab your multimeter tips and do the next
Here
disconnect these
connect here
and the other tip here
so now
my multimeter tips are part of the Power Supply now
here I have
my multimeter tips ready to make ground touch ground
and the other touches the positive line
What are we going to do?
I'll take my negative tip and touch ground anywhere
okay? Anywhere
and the positive
touching the positive line, on any capacitor
What will happen to the current?
I'm going to inject current to this line
and it will heat up the bad capacitor
Just like that
this can be applied to any line that you find leaking
or any shorted line
this VDD_BOOST line
as we can see, it has a voltage of 3.8 volts, we can inject all the current
What if you don't know what the line capacity is?
Start with 1 volt and 1 amp
then increase it
1.5 amp, 2 amps
3 amps
okay?
And keep looking for the guilty
this is very easy, look
I'm doing the next
I took my multimeter and put one tip in negative
either side of the negative
and the positive I can put it in this capacitor
what I'm doing is exactly what I'm doing in the drawing
I'm putting one tip of the multimeter to the line
and one tip to ground
to find the bastard who is short-circuiting the line
so
it's just like that
as I said, this can be used for leaking lines
and
shorted lines, as in this case
okay?
So
once frozen what do I have to do?
I just put
negative in negative
and positive in the positive capacitor
now let's wait, this is set at 1 amp, is not that much
wait a moment
probably 1 amp... oh wait, there it is
the bastard is discovering himself on his own
Did you see it?
This bastard is short-circuited
You see?
With 1 amp
What to do now?
Just remove it
Let's see if this one was the culprit
now with the multimeter
in continuity mode touch here
Look, a capacitor
should never have... what?
Continuity
Okay, since we saw that bastard
was short-circuited
now let's see if the phone turns on
Let's see
and there it is, we have
the phone turning on
all due to a capacitor on a main line that was shorted out
If you noticed, is something very easy
inject voltage in a line to find a short circuit
either in a capacitor or in a circuit, it's the same process
What would have happened if
for example, this one
this already turned on
What would have happened if for example
if this had been an IC
the same would have happened with the current
the current comes
and heats up this bastard
So
this was a little contribution, as I said, a short video
something to keep in mind for all those who are just starting out
and for those who were confused about it
I hope this has helped you and clarified many doubts
I'm trying to remember if I forgot something to tell you
If I forgot something to take it in mind with this example
and see if I'm explaining myself well, but I hope you have understood
it was just an initial consumption
connected it and short-circuited it
Okay? A short in a main line, we already know that iPhone 7
has 3 main lines, so I started touching battery
it's not shorted, touched VDD_MAIN, nothing
touched VDD_BOOST, there's a short
was heating a circuit, now you know that not everything that heats up is the problem
And what did we do? Inject voltage
and that's all
what would have happened if the consumption was AFTER turning it on?
So that would have been secondary consumption
All lines after the PMIC onwards, measure them one by one
find the shorted one, inject voltage and that's it
So gentlemen, it is always a pleasure for me to contribute here
it was a pleasure to come and greet you, today we're going to take a break of the lessons
Tomorrow we're going to have a lesson again
there are only about 10 lessons left
so we can finish with the Module 1
The truth is that I am very busy, here we've been
updating much of the website content
registration will be open soon
you'll see what we have for you
For me is always a pleasure, take care and we'll see you soon
Bye!