MacBook Pro A1707 820-00281 No Power – Finding Short on PP3V3_S4 Line Using Thermal Camera – AppleFix & Tech Engineers

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Macbook LogicBoard Repair

MacBook Pro A1707 820-00281 No Power – Finding Short on PP3V3_S4 Line Using Thermal Camera

If your MacBook Pro A1707 (820-00281) shows no power or no response, chances are you’re dealing with a shorted PP3V3_S4 or PP3V3_S5 rail. These lines are crucial for the system’s power sequence, and a short can cause no power on MacBook Pro 15″ logic boards. In this article, we’ll explore how to use a thermal camera to identify faulty components and discuss a real-world case where UB203 was getting hot—but the actual fault was somewhere else.

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Step 1: Understanding the Power Rails

The PP3V3_S4 and PP3V3_S5 lines supply 3.3V to various logic and controller circuits. When either line is shorted, the MacBook will not power on. Using a multimeter in diode mode, you can confirm if a line is shorted to ground. A reading near zero indicates a short.

Step 2: Using a Thermal Camera for Diagnosis

When a logic board has multiple shorted lines, it can be tricky to find the source of the problem. A thermal camera is an essential diagnostic tool for MacBook logic board repair.

1. Inject low voltage (1V–3V) with a current-limited power supply into the shorted line (for example, PP3V3_S4).
2. Observe the board through a thermal camera — the faulty component will usually heat up rapidly.
3. Be careful not to overheat the board; excessive voltage can damage other ICs.

In many cases, you may notice UB203 (a power management IC) getting hot. However, that doesn’t always mean UB203 is the culprit — it might be conducting heat from another component located on the same power rail.

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Step 3: Common Traps – When UB203 Isn’t the Real Fault

In our MacBook Pro 820-00281 repair case, UB203 appeared to be shorted under the thermal camera, but the actual faulty part was a tiny capacitor near the SMC area. After removing and testing nearby capacitors, we found one with internal shorting. Replacing it restored the PP3V3_S4 line and brought the MacBook back to life.
This highlights why relying on heat signature alone can mislead technicians — use both schematics and boardview files to trace each power line and test nearby components.

Step 4: Why Choose AppleFix Hamilton

At AppleFix Hamilton, we specialize in advanced MacBook logic board repair and microsoldering. Whether it’s a shorted PP3V3_S4, no power issue, or corrosion damage, our MacBook repair experts in Hamilton, New Zealand can bring your device back to life.
📍 Visit us at 937 Victoria Street, Hamilton, New Zealand
📞 Call 07 839 4111
📧 Email: support@applefix.co.nz