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Apple MacBook Pro 13” A1278 Slow running,Fan crazy Repair  


Hassan Al-sayed Ali
Member Admin
Joined: 1 year ago
Posts: 118
04/01/2020 10:09 am  

Exclusive on the Global Mobile Forum

Apple MacBook Pro 13” A1278 Slow running,Fan crazy Repair

Machine model: A1278

Board number: J30 820-3115

Symptom: Slow running, fan running wildly

Maintenance process:

The machine enters the system to test the system running slowly, the fan runs wild, disassemble the machine to check that the motherboard has not been repaired, and there is no water. Cause to run

Slow and fan rotation is usually the abnormal temperature control of the motherboard detected by the EC.

Listed as:

As shown in Figure 30-1, the EC reads temperature control information through the 9 / 10-pin SMBUS bus of the U5511. The I2C bus in the circuit

Problems, abnormal temperature detection by the temperature control chip can cause slow operation and fan rotation.

Figure 30-2 shows a group of SMBUS buses in the EC. Problems with this SMSBUS bus will also cause slow running,

The fan runs wildly, because the trackpad (touchpad) has a set of temperature control circuits, so the EC cannot be detected without the touchpad.

Temperature information on the touchpad can also cause slow operation and fan malfunction.

As shown in Figure 30-3, the EC reads the CPU temperature information through PECI. This abnormal signal will also cause slow running and fan

Crazy turn failure. This is the example. In general, such faults are checked in the EC temperature control test. Of course, the EC body is also bad.

There is a certain chance.

Back to this motherboard repair, after examining the above examples one by one, it was found that CPU_PECI has no waveform.

Inspection of the motherboard found that as shown in Figure 30-4, the resistor R5054 had a slight corrosion phenomenon. The corrosion resistor was repaired and the fault was repaired. Such as

Figure 30-5 shows the normal CPU_PECI waveform.

The final installation tests were normal. As shown in Figure 30-6, the machine was successfully repaired.


Figure 30-1   Temperature control circuit U5511



Figure 30-2   EC SMBUS reading touchpad temperature



Figure 30-3   EC reads CPU temperature information through CPU_PECI



Figure 30-4  CPU_PECI resistor R5054 slightly corroded

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