Component MacBook Repair: Power Supply Repair
This article will discuss methods for diagnosing and repairing power supply circuit faults. As an example, consider a typical crash of a MacBook Unibody 13 ”(A1278 2008)
The following case is a very frequent malfunction for this model: Mac suddenly stops working from the power supply, the indicator does not light up on the plug, the battery does not charge. At first glance, it is very similar that the power supply unit “burned out”. Replacing the power supply does not help. And thus, the MacBook works until the battery is exhausted. After that, it will not turn on.
At first glance, this malfunction is not difficult, because if the Mac is working normally from a charged battery, the conclusion is that all the main circuits and components are intact, and the fact is that the voltage from the unit simply does not reach the board (from the series that any Any fuse or element on the input power circuit). If a person has more or less necessary knowledge of electronics, he will disassemble the MacBook, take a tester and begin to measure the voltage on the board, and then it turns out that everything is not so simple: the necessary voltages are present, but the Mac still does not work from the unit. Why is this happening?
The thing is ... Apple uses intelligent power supplies in their laptops, which means that, in addition to the supply voltage, there is an information channel. In the plug of the unit there is a microcircuit which “communicates” with the multicontroller (SMC) on the motherboard. The microcircuit has a memory area in which the data about the block is written (manufacturer, serial number, power, etc.), and until the Mac reads this information, it will not work from the block.
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Thus, the cause of our breakdown is the breaking of the block - multicontroller (SMC) connection, and the repair is the restoration of this circuit. To repair this level, you need a schematic diagram of the motherboard. The figure shows the part of the circuit responsible for this circuit. Consider it in more detail.
Big scheme tyts .
The information signal ADAPTER SENSE through the protective zero resistor R6928 falls on the transient dual transistor Q6920, and from it goes already to the multi-controller (SMC). The transistor is controlled through a chain consisting of transistors Q6910, Q6915 and the comparator U6915. Such a sophisticated information signal transmission circuitry performs a protective function. The downside of it is that the burning of any element will lead to the rupture of communication.
Diagnostics and repair are reduced to the definition of a burned-out element and the subsequent replacement. It does not make sense to talk in more detail about this, since these methods are obvious to a specialist, it is enough to have a scheme, and for people who never hold a soldering iron in their hands, there is absolutely nothing to do under the bottom cover of the MacBook. It is worth noting that the dual transistor Q6910 (observation from practice) often burns out. It is located along the input power circuit, so a voltage surge or static discharge when connecting a unit can “burn” it. In the worst case, the multicontroller may burn.
The difficulty is that “cartoons” in poppies have their own firmware, and if you replace it with a new one, it will be “empty” and will not work. Consider the firmware, as far as I know, so far no one has succeeded, and there is no place to take it either. Thus, for the repair you will need a fee "donor" with a working cartoon.
The following case is a very frequent malfunction for this model: Mac suddenly stops working from the power supply, the indicator does not light up on the plug, the battery does not charge. At first glance, it is very similar that the power supply unit “burned out”. Replacing the power supply does not help. And thus, the MacBook works until the battery is exhausted. After that, it will not turn on.
At first glance, this malfunction is not difficult, because if the Mac is working normally from a charged battery, the conclusion is that all the main circuits and components are intact, and the fact is that the voltage from the unit simply does not reach the board (from the series that any Any fuse or element on the input power circuit). If a person has more or less necessary knowledge of electronics, he will disassemble the MacBook, take a tester and begin to measure the voltage on the board, and then it turns out that everything is not so simple: the necessary voltages are present, but the Mac still does not work from the unit. Why is this happening?
The thing is ... Apple uses intelligent power supplies in their laptops, which means that, in addition to the supply voltage, there is an information channel. In the plug of the unit there is a microcircuit which “communicates” with the multicontroller (SMC) on the motherboard. The microcircuit has a memory area in which the data about the block is written (manufacturer, serial number, power, etc.), and until the Mac reads this information, it will not work from the block.
')
Thus, the cause of our breakdown is the breaking of the block - multicontroller (SMC) connection, and the repair is the restoration of this circuit. To repair this level, you need a schematic diagram of the motherboard. The figure shows the part of the circuit responsible for this circuit. Consider it in more detail.
Big scheme tyts .
The information signal ADAPTER SENSE through the protective zero resistor R6928 falls on the transient dual transistor Q6920, and from it goes already to the multi-controller (SMC). The transistor is controlled through a chain consisting of transistors Q6910, Q6915 and the comparator U6915. Such a sophisticated information signal transmission circuitry performs a protective function. The downside of it is that the burning of any element will lead to the rupture of communication.
Diagnostics and repair are reduced to the definition of a burned-out element and the subsequent replacement. It does not make sense to talk in more detail about this, since these methods are obvious to a specialist, it is enough to have a scheme, and for people who never hold a soldering iron in their hands, there is absolutely nothing to do under the bottom cover of the MacBook. It is worth noting that the dual transistor Q6910 (observation from practice) often burns out. It is located along the input power circuit, so a voltage surge or static discharge when connecting a unit can “burn” it. In the worst case, the multicontroller may burn.
The difficulty is that “cartoons” in poppies have their own firmware, and if you replace it with a new one, it will be “empty” and will not work. Consider the firmware, as far as I know, so far no one has succeeded, and there is no place to take it either. Thus, for the repair you will need a fee "donor" with a working cartoon.
Source: https://habr.com/ru/post/156271/
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