The MacBook had been damaged by water and had been cleaned by a local computer store in Queensland but still not working. The owner was told the logic board is faulty and the MacBook cannot be repaired. MacBook Model Number A1398 Year 2012 and Logic board Number 820-3332.
The logic board is nice and clean, good work! Save our time to clean. We connect it to a power supply and the fans spin but no chime no display. All the power rails are present except the CPU core power.
The CPU power management chip u7400 is responsible for creating CPU core power as shown below:
S0 state power rail PP5V_S0_CPUIMVP_VCC provides power to the three modules VCC, VDDA, VDDB of chip u7400.
System Management Controller (SMC) sends CPUIMVP_VR_ON to enable u7400.
R7402, R7403 set the working mode of u7400 as CPUIMVP_TONA and CPUIMVP_TONB.
CPU uses SVID bus CPU_VIDSOUT, CPU_VIDSCLK and CPU_VIDALERT_L to send CPU identification to u7400, and u7400 outputs CPU core power voltage PPVCORE_S0_CPU corresponding to the CPU ID.
During POST (Power On Sefl Test), CPU sends a second SVID signal to u7400 to adjust the CPU core power voltage.
Once booting into MacOS, CPU keeps communicating with u7400 to modify the core power dynamically corresponding to the load of the application software.
Check pin 47 chip enable signal CPUIMVP_VR_ON, ok.
Check pin 46, 29, 19 VCC, VDDA, VDDB power supply to the chip, all ok.
Check pin 1 chip mode setting CPUIMVP_TONB, not ok.
Check resistor R7403, open line.
Replace R7403 with a new 182K resistor, CPU Vcore power is present!
The mac is working again.
The mac is tested by Apple Service Diagnostics (ASD) software dedicated to this model.
Note: u7400 is the chip number on Apple logic board electronic circuit diagrams (schematic 820-3332).
The test of good customer service is when things go a bit wrong. There was some confusion about one aspect of my repair and Frances resolved the problem effortlessly and with a smile. You can place your trust in this organisation company. Excellent! They care about their reputation, which is a great thing.
1 month ago
It-Tech Online did a fabulous job on my MacBook Pro repair. Frances was very clear about how to fix the issues I had, how much it would cost and how long it would take. The repair was on budget, turned around within a couple of days as discussed and I have my computer improved and working better than before. I would recommend Frances and her team very highly.
2 months ago
Absolutely fantastic experience. You'll be provided not only their professional repair service, but also free but still professional education on how to make the best of your devices and how to properly look after your gadgets. Will definitely be a loyal returning customer,
5 months ago
I had a great experience getting my water damaged Macbook Air (2015) fixed here. I was able to mail my laptop to Frances to get it checked out and repaired. Once I sent it (from around Doreen area to her shop in Bentleigh East) it took less than a week for her to find out what was wrong, get the necessary parts and fully repair my laptop and then send it back to me. The correspondence was very friendly and professional and I am going to definitely recommend this service to anyone that needs it!
6 months ago
I had a GPU fault on my Macbook Pro which made it shut down at odd times and finally it would not boot at all. I was very sad. I spoke to Frances on the phone, she walked me through the repair process and the price, everything was very clearly communicated. I posted my Macbook Pro to Frances that day, she fixed it and now I am writing this review on my amazingly resurrected Macbook :-) Now I am very happy again.
Thank you Frances, you are amazing
7 months ago
What a great shop! Francis is amazing, her attitude and energy to help is excellent. Took two macbooks in for repairs and upgrades after being told by another shop to replace. Could not be happier, its been a few months and they have not skipped a beat.
This is easily the best experience I have ever had with a business, cannot fault it.
Thanks so much!