Guys! How are you? Edgar here welcoming you all with this new video
I often come in here to my workshop to repair a lot
only repair
and sometimes I find some fault that I say "Why didn't I record a video about it?"
if I had recorded, we would have had a very nice video to share
but as I explained before, I am very busy repairing that it is difficult to me to record a video
because it would take me longer
so, suddenly you'll see these kind of videos where I just give the diagnosis I made and the repair
I know that you don't like those videos, I know you'd rather see me doing the whole diagnosis, but
it's better to share it like this, and
from time to time I will make these videos
the important thing here is that I want to share it so that our experience grows more
so, a client left me this iPhone, let's go here
left me this iPhone 8 Plus
that neither the fingerprint nor the touch worked
I already repaired it
021019
if you notice, the touch works perfectly and the fingerprint
So, I'll tell you the whole diagnosis
It turns out that if this phone was connected to a Chinese display or a very poor quality display
the touch worked, but not the fingerprint
the fingerprint was simply not detected
something very very weird, now
when we connected it to an original display
and connected the display and the fingerprint, automatically everything was automatically locked
when I disconnected the fingerprint from the motherboard
the touch worked
it was something very weird
because the touch worked with this chinese display, I checked if
it detected the fingerprint with 3uTools
so, I opened 3uTools
and I noticed it didn't detected the serial number of the fingerprint with this display
I tried with a fingerprint that I have from an original display that I know 100% it works
I put it with this chinese display and it didn't detect the fingerprint either
therefore, if this display didn't detect the two fingerprints, it means that the problem was in the board
so, I started, let's see this, I looked for the fingerprint connector
I started to look at everything, it has it's voltage drops, the voltage was fine without connecting it, now
something very curious got into my head to tell me "this is weird"
just look at this, if we know
the display has this connector, this little connector here
is the fingerprint connector
if I disconnected the fingerprint from here
and connected this one, only this, without connecting the fingerprint here
was enough for my touch to be locked
how is possible that only the connector placed there, without anything to be powered
there was nothing
locks the touch?
but if I disconnected the fingerprint connector from the board, the touch worked
I hope you're understanding
I connected the display fingerprint connector to the board, but disconnected the fingerprint
it's as if the fingerprint is not connected
but still it was enough to lock the touch
how weird
anyways, let's continue
what I found here was that I measured everything
and had everything except something very very weird
this voltage from here
is a voltage of 1.8 Touch
this 1.8 Touch, if we trace it back to find out where it comes from
this is an LDO
sent by PMIC, and sends it to this filter
before entering the filter, it passes through a circuit
to U5890
this LDO
I already have it recognized, because I know that it many times blocks the touch when connecting the fingerprint
So, let's look for the component U5890
tap Enter, Enter, Enter
Ok, here we are, Mesa, Mesa, this one is Power
Now, how this circuit works? It's pretty easy, this circuit
is powered by VDD_BOOST
and when I turn on this phone and this LDO is generated
that goes to my display
it goes there, but it also goes to the fingerprint connector
this tension is divided into 3
but it's the same voltage
if you notice, it turns on
Enable is generated, and then regulates this voltage and gives me an output of 2.75 volts, perfect
I measure that voltage at its output, before it is divided into 3
so, where I can measure it?
Here, look, why is it divided into 3?
because it goes here and here and here
ok? 3 places
we could say 4 places
so, before dividing I measure it here
exactly in this filter, I measure it
I turn on the phone and there is 1.8 volts
then it dissapears, in the second stage of turning on it appears again 1.8
but when the phone is on, the 1.8 in the second stage of turning on drops into 200mV
very weird
I'm doing that measurement with the display connected
because if it is not connected, there is no powering
with the display and fingerprint connected
now I'll try without connecting the fingerprint
I'm looking at the 1.8, it stays stable, dissapears
appears again and it doesn't drop to 200mV
Well
So, I say the problem will be in this connector
it could be this one, this, this, this
or LDO
because LDO turns on this one and shows this voltage
Now, this fault I already have it recognized to that LDO
I've had many iPhone 8 that
when the touch doesn't work when connecting the fingerprint
I remove that LDO because I've also seen the 1.8 altered
So, I remove the LDO and replace it
look once again and there's the same
1.8 drops to 200mV when the phone is on
something very very weird
another thing is, I'm measuring here
in the turning on and I have 2.75 volts
here I have 1.8, everything is there, but when it finishes turning on for some reason, it goes down
To keep this short
I measured everything, measured voltage, I2C lines, measured reset signals
synchronization signals, everything related to the display and the fingerprint
I tried with many fingerprints and it just didn't work
so I went back to the point where this got weird in my head
where I had this in my head and said
"Why a simple connector will lock the touch even if I don't connect anything, why?"
Why it would lock the touch? If it is only the connector
it is as if I
connected one of these
it is as if I connected one of these
if I connect an iBridge
and don't connect anything from here, it's like it is only placed there, there's nothing
but why it locks the touch if it is only connected
so I said "this has to be the connector"
this has to be the connector
remove the connector, put another one, assembly the phone, connect the display, connect the fingerprint
and BINGO, the phone is working perfectly again
Now, this for us is difficult to explain
it's difficult to explain because, the connector was not damaged, broken, burnt, misplaced, NOTHING
the connector looks good
I checked the solder on the sides and everything seems to be fine
for some reason, when something was connected to this connector
even if the fingerprint wasn't connected to the display, it was enough to alter this 1.8 volts
and left me the touch without working and the fingerprint without being recognized
This kind of faults are pretty, it's where experience will help us
because, if I know the touch needs this list of things to work
if the fingerprint needs these things to work
and if these 2 lists that are needed to work are fine
there are no shorts or leaks, there's nothing here
then we have to act in cases like these and say "Well, it is the connector, there's nothing else"
if it wasn't the connector, I have no idea what else I could probably be checked, probably...
I don't know, I would have loaded software on the phone, I don't know
but we just removed the connector and it worked
these kind of faults are pretty, sadly as I said, sometimes I don't have time to record them
and that's why I'm bringing them in this moment
with these kind of videos
from time to time expect these types of videos where I'll just be explaining the diagnosis
because as I said, sometimes I'm very busy and I can't record pretty faults like this one
but it's very important that I share it, so that our library of experiences can grow more
and we realize many things
the important thing here is to know how everything works
know how the touch works, know how the fingerprint works
if I know the touch needs powering, SPI lines, reset signal, etc, and everything is there
why shouldn't it work?
if the fingerprint needs this and it has it, why shouldn't it work?
Why if I have everything shouldn't it work?
Well, the peripheral is connected to the connector, what if that alters it?
And it was the problem, this is the second time
that I've done this type of faults
previously I had an iPhone 6S Plus without touch
everything was fine, replaced the connector and it worked
So, we must be careful with these faults
follow me in my social media, don't forget to share these videos, leave your like and subscribe to my channel
and share these videos so our beautiful community can grow even more
I know you prefer the longer videos, but it's better to share these types of videos than not to share anything at all
from time to time, I won't always bring this kind of videos, but from time to time I will
So here I say goodbye
take care and we'll see you in the next video
Bye!