iPad won’t turn on

 Максим Исаев

 Reading time: 2 min

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iPad diagnostics

iPad won’t turn on

iPad diagnostics

During the training of bga soldering, one of our students brought with him a client iPad 2017, which won’t not turn on.

First, we performed the initial diagnosis of the device.

For this, iPad was connected to a laptop in order to exclude that the tablet is in recovery mode (DFU).

The tablet was not detected by the laptop.

It was decided to disassemble the tablet and sequentially disconnect the touchscreen and display from the case for further diagnosis.

A separator was used to prevent damage to the sensor.

When disassembling, pay attention to the lower right part of the touchscreen, there are ribbon cables of the sensor, Home button and display.

Set the temperature to not more than 70 degrees Celsius on the separator.

iPad won’t turn on

Then we removed the tablet motherboard from the tablet body.

Since the board is glued on tape to the tablet body, a separator was also used to remove it.

Next, we measured the resistance in the primary power circuit, on the battery connector using a multimeter.

The multimeter showed a kilo resistance in the circuit PP_BATT_VCC. This indicates that there is no short circuit in the chain.

The next step when the “iPad won’t turn on” is to measure the resistance in the secondary power supply circuit of the iPad 2017.

To do this, we measured the resistance on the inductor (below in the screenshot). The multimeter readings are 1 ohm. This means a short circuit in this circuit. In a working circuit, the resistance should be kilo-ohm.

Замер сопротивления во вторичной цепи питания — Measurement of resistance in the secondary power circuit

To search for a short circuit in PP_VCC_MAIN, voltage was supplied from the LBP to this line after removing the transistor.

Транзистор в цепи PP_VCC_MAIN — PP_VCC_MAIN transistor

Using FREEZER we detected a heating capacitor.

Visual inspection of the capacitor clearly showed damage of the tablet body.

We dismantled this capacitor using a PS-900, and measured the resistance at PP_VCC_MAIN. Resistance has risen to kilo ohms, which means that the short circuit is eliminated.

A capacitor was taken from the donor board iPad 2017 and installed on the board being repaired.

The next step is to install the transistor on the board.

We installed the board in the tablet case and turned on the device.

iPad turned on, so repair completed.