The Problem

The Mac did not boot reliably. Most of the time, it drew around 0.51A and stayed there. Sometimes, it would chime once, proving that the board was not completely dead.

When we checked the power rails, one important rail was missing:

 
PPCPUVTT_S0 = 0V
ALL_SYS_PWRGD = 0V
 

This meant the Mac could not complete the system power-good sequence. Without that sequence, the machine could not boot normally.

Oscilloscope waveform showing PPCPUVTT_S0_REG_R rising and then collapsing during CPUVTT regulator startup.
Before the repair, the CPUVTT output tried to start but collapsed because the regulator sense path was incorrect.

Why This Was Not a Simple Repair

Many no-power repairs are caused by a shorted capacitor, a failed power chip, or liquid damage around a major rail. This case was more difficult because the CPUVTT regulator was trying to start, then shutting down.

Several parts were checked and replaced during diagnosis:

 
U7600 CPUVTT regulator
C7631 bootstrap capacitor
R7640 current-sense resistor
Q7630 and Q7635 MOSFETs
CPU load side isolated for testing
 

Even after these checks, the CPUVTT rail still started and collapsed.

Oscilloscope waveform of CPUVTTS0_VBST bootstrap voltage during CPUVTT regulator startup.
The bootstrap signal was checked while diagnosing why the CPUVTT regulator started and then shut down.

The Real Cause

The breakthrough came from checking the small zero-ohm sense resistors near the CPUVTT regulator.

One of them, R7641, was not reading as a proper 0Ω link. It measured around 40Ω.

That small resistance was enough to confuse the regulator feedback path. The regulator started, detected the wrong condition, and shut itself down.

We replaced both:

 
R7641
R7642
 

After that, the Mac chimed every time.

A Second Fault: Chime but Black Screen

After the no-power fault was fixed, the Mac started reliably and Caps Lock responded, but the screen was still black.

This pointed to a display or GPU-related issue. On this model, a common failure is the capacitor on the GPU framebuffer 1.8V rail. As the capacitor loses capacity, the rail becomes unstable and the Mac may boot with no display.

The failed capacitor was:

 
C9560
Rail: PP1V8_S0GPU_ISNS_R
 

We replaced C9560 with a new 220µF or 330µF polymer tantalum capacitor.

The display came back immediately, and the Mac became fully functional.

Customer-friendly infographic showing how IT-Tech Online repaired a 2010 17-inch MacBook Pro with no power, CPUVTT regulator failure, black screen, and GPU framebuffer capacitor issue.
This rare 17-inch MacBook Pro was saved by diagnosing two separate logic board faults instead of replacing the whole machine.

Final Result

This repair required finding two separate faults:

 
Fault 1:
Intermittent no power / 0.51A stuck
Cause: R7641/R7642 CPUVTT sense path issue
Fix: Replace R7641 and R7642

Fault 2:
Chime but black screen
Cause: Weak C9560 on GPU framebuffer 1.8V rail
Fix: Replace C9560 with new polymer tantalum capacitor
 

The 17-inch MacBook Pro now boots, displays normally, and is fully working again.

Why Customers Choose IT-Tech Online

Some Macs are worth saving, even when they are old. The 17-inch MacBook Pro is a perfect example. It has a large display, solid build quality, and many owners still prefer it over newer models.

At IT-Tech Online, we do not simply replace the whole logic board when one small circuit fails. We diagnose the board, measure the rails, check the power sequence, and repair the failed components.

That is how this 2010 17-inch MacBook Pro was saved.

This repair shows one example of how we help customers recover their Mac instead of replacing it. See more completed Mac repair cases here:
Successful Mac Repair Cases

Need help with a dead MacBook, black screen, or logic board fault?

IT-Tech Online provides component-level Mac logic board repair in Melbourne and accepts mail-in repairs Australia-wide.

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