We got an iPhone 6S from customer, the
problem is the rear camera cannot be used after water damaged for a
sometime. We replace the new camera, but the problem still the same, so we
remove the motherboard and start to repair. Observing it under a microscope, and we found that power supply pipe of
rear camera was been burnt down, as shown in picture 9-1-1, take out it
directly. This chip is converted to 2.85V by main power supply chip VCC_MAIN,
and then to rear camera, it supply power to front and rear camera on iPhone 6,
but it only supply power to rear camera on iPhone 6S.
After take out the chip, we found the pin
of main power supply was been burnt down. Because this chip is too small and
hard to replace, direct short connect is also undesirable and unstable, night
photography is not clear, so we want to borrow 3V voltage to here. We heard
there is a 3V test point on the motherboard which near the middle plate iPhone screws. But there are four test points, and we're
not sure which one. We shave one and then turn it on, measure it with multimeter, we found this one is the 3V test point.
As shown in picture 9-1-2.
Solder a jump wire on it, as shown in picture 9-1-3.
After test, it can take pictures. Apply green UV oil and assemble iPhone.
What's surprising is that the customer
sends the phone back on the next day, and he said all was fine at the
beginning, but the phone was in serious heat at night, and then it cannot turn
on. Why is that?
Measure it with multimeter,
it shows large currents directly, the
resistance value of iPhone battery interface is normal, which means the main
power supply short circuit, most of this
is caused by the breakdown of the capacitor. So we're still going to follow the
routine burning process to repair. Apply rosin on the position of main power
supply, and then start to burn. Many peers use 2A power multimeter to do it,
but direct burning doesn't work. You can use battery which in mobile power
supplies to do it, as shown in picture 9-1-4.
One side connect machine, one side connect
the position which is short circuit, but until the tin wires were melted, there
was still no change on the back of the iPhone motherboard.
Look at the front of motherboard, we found a little black which in the
place of fix the camera problem. Check it more carefully, we found this point
was burnt out; the PCB board also was burnt. There was a lot of black dust when
we shave with scraper blade, that's why the phone is so hot. Seriously
clean the circuit, but the resistance is still low. We need to keep cleaning it
up, so we continue cleaning it under the microscope,
until the short circuit problem disappears.
Apply the green UV oil on this point, after
baking it with the UV glue ultraviolet light, we install the camera 3V on it. We're
worried that the motherboard is still hydrated, so we bake it at 130 degrees on
the heating platform. At the end, assemble the iPhone and send
back to customer.
Summary
When you are going to fixing cellphone
which suffers from water damage, there are likely to be squealed. You have to
vaccinate your customer in advance to inform them of the danger. Otherwise, you
may face the risk of compensating your customer's cell phone.
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