Starting point

This console also had some repair history. The Blu-ray drive had previously been replaced, but replacing the drive did not resolve the power problem. Because of that, I wanted to start from the beginning rather than assuming the previous repair attempt was related to the main fault.

The goal for this first diagnostic session was simple: check the basic power circuitry, rule out obvious shorts, establish how far the console gets through its startup sequence, and use UART error logging to narrow down the problem.

Initial fuse checks

With the motherboard removed, I started by checking the fuses around the EDM-020 board.

Everything tested normally except F5401. Under the microscope, F5401 definitely appeared to be open. This was immediately interesting because the console had previously had Blu-ray drive work.

I checked resistance to ground on both sides of F5401. One side climbed into the tens of megaohms and the opposite side appeared effectively open to ground. There was no obvious low-resistance short sitting behind the failed fuse.

Later in the session, I replaced F5401 with a new fuse. The console's behaviour did not change. It still produced the same single-beep startup attempt and shutdown. Importantly, the replacement fuse did not blow during testing.

That suggests the original fuse failure was likely a separate issue rather than the direct cause of the current single-beep fault.

Initial short checks

I then checked the major inductors and power rails using resistance and diode measurements. Nothing immediately stood out as a dead short.

With an APU such as the PS5's, it is important not to assume that a low resistance on VCORE automatically means a short. Modern CPU and GPU core rails naturally have very low resistance because thousands of transistor structures sit across the supply.

Later measurements on one bank of VCORE inductors gave approximately 0.69 ohms, 1.3 ohms, 0.94 ohms, 0.94 ohms, 1.3 ohms, and 2.3 ohms. None of those measurements looked like an obvious catastrophic short by themselves.

Bench power supply testing

The motherboard was powered from a bench supply at 12 V. Initially the current limit was set around 700 mA, but the console needed more current to attempt startup, so I increased the available current and watched the startup profile.

One observed sequence was approximately:

22 mA to 100 mA to 295 mA to 30 mA to 0 mA

With a higher current limit, later startup attempts reached about 1.8 A and one attempt reached around 2.2 A.

The bench supply itself was not entering current limit and was not shutting down. The console was choosing to stop drawing power. If the board had a large short, I would expect the supply to clamp, voltage to collapse, or current to stay high. Instead, the PS5 powers circuitry for a short period and then deliberately shuts itself down.

Standby rail measurements

Before going deeper, I checked the easily accessible standby rails. I found 5 V, 3.3 V, approximately 1.15 V, and approximately 1.9 V.

I then monitored those rails during startup. The 5 V, 3.3 V, 1.15 V and 1.9 V rails remained present and stable, which eliminated a lot of the basic standby troubleshooting path.

VCORE appears during startup

One of the most important findings came when measuring the APU VCORE circuitry. On the APU side of the VCORE inductors, I could catch the core voltage briefly coming up.

Typical measurements were around 0.6 V to 0.9 V. Depending on the startup attempt, I saw roughly 600 mV, 700 mV, 800 mV and occasionally around 900 mV.

Initially it looked as though some inductors were producing voltage and others were not. After repeating the test, I realised every second power-button press was effectively toggling between an actual startup attempt and the alternate state. Once that was accounted for, all of the VCORE inductors examined could produce the expected brief core voltage.

Connecting UART

At this point it made sense to stop blindly probing the board and get UART working. This was my first proper successful use of PS5 UART diagnostics.

The first adapter I tried was based on a CH340. It worked as a serial adapter, but its transmit line was sitting at approximately 5 V. That explained a weird symptom: when only the receiving side was connected, the console behaved normally, but connecting the adapter's transmit line changed the console's power behaviour. That adapter was removed.

I switched to a CP2102 USB-to-UART adapter and verified its logic level was approximately 3.3 V before connecting it to the PS5. After manually installing the Silicon Labs driver, Windows detected it correctly and communication was established using the PS5 service software.

UART error log

The most recent relevant errors repeatedly showed two severe faults:

The CPU entry specifically reports an SoC VRM failure and refers to the APU VRM / Infineon XDPE14286A PWM controller. These CPU and GFX VRM fault codes appear repeatedly throughout the log.

The broader power-sequence entry lists possible categories such as peripheral, GDDR6, APU and data-line faults. I do not believe that log entry alone justifies pulling memory chips. The repeated CPU and GFX VRM fault entries are much more interesting.

Oscilloscope testing VCORE

Because UART was reporting VRM-related failures, I wanted to see what VCORE was actually doing rather than relying only on the slower multimeter. I connected an oscilloscope to the APU side of one VCORE inductor.

VCORE rose cleanly to roughly the expected core-voltage region, stayed present for a few hundred milliseconds, and then fell cleanly back to zero.

That was a very important observation. The VCORE regulator is not simply dead. It starts, produces core voltage, holds it briefly, and then the system shuts it down.

I also checked the main 12 V input feeding the VCORE power stages. The 12 V rail stayed completely stable while VCORE came up and disappeared. VCORE was not disappearing because the VRM lost its 12 V input.

Probing the MOSFET / switching side of the VCORE inductor showed the switching node active during the same period VCORE existed, then stopping when the console shut down. Again, that argues against a completely dead VCORE regulator.

Power-on rail survey

Because the basic VRM appeared to function during the startup window, I changed strategy and began checking the switched power rails one by one. The aim was to find a rail that never appears, appears at the wrong voltage, or disappears significantly earlier than the rest of the system.

A switched rail expected around 1.1 V came up correctly during startup and disappeared when the console shut down. The HDMI area had the expected supplies including 5 V and other listed rails. The HDMI connector had been pushed inward slightly, but the pins still appeared attached under the microscope and I could not see obvious physical damage.

VMEM, the GDDR6 memory supply, measured approximately 1.35 V. It appeared correctly during startup and disappeared when the console shut down. That does not eliminate every possible GDDR6 fault, but it means there is currently no evidence that the PS5 simply lacks its main 1.35 V memory rail.

The SSD regulator output, expected around 2.5 V, initially measured 0 V. For a moment that looked interesting, but the ground clip had fallen off. Once the measurement ground was restored, the 2.5 V rail was present correctly.

Where the diagnosis currently stands

At the end of this first session, the PS5 is not repaired, but the fault has been narrowed down considerably.

• The board receives 12 V correctly.
• There is no obvious hard short across the main APU VCORE network.
• All checked fuses now test correctly after replacing F5401.
• The replacement F5401 fuse survives power-on and does not blow.
• The standby supplies tested so far are present.
• The PS5 progresses into its main startup sequence and can draw about 1.8-2.2 A.
• The power supply is not entering protection. The console initiates shutdown.
• VCORE comes up to approximately 0.6-0.9 V.
• The 12 V supply feeding the VCORE stages remains stable.
• VMEM at approximately 1.35 V comes up.
• The SSD 2.5 V rail comes up.
• UART repeatedly records CPU and GFX SoC VRM power failures.
• UART also repeatedly records that the APU is not responding during initialization.

Current working theory

At this stage, I think the board is getting reasonably far into the startup sequence before something fails validation and causes an orderly shutdown.

This does not currently behave like a simple shorted capacitor on a main rail. It also does not behave like a completely dead VCORE regulator. The console enables the APU power system, memory power appears, core voltage appears, and substantial current is drawn. Something then prevents the APU startup sequence from completing.

The UART records that condition as CPU / GFX VRM failure and APU non-response, but whether that is the cause or the result of another initialization failure remains to be determined. The possibility of an APU fault is still on the table, but there is not enough evidence to condemn the APU yet.

Replacing F5401 also helps separate the Blu-ray-side fault from the main issue. The fuse has been replaced, survives power-on, and made no change to the console's behaviour.