This Samsung S23 Ultra came to us with a single complaint: it wouldn't charge. However, what we discovered inside turned it into one of our most technically complex cases, with a solution that may surprise you.

What You'll Need for This Repair

Step 1: Initial Diagnosis — Connect the USB-C Test Board

The first step in any charging fault is to avoid assumptions. We connected a USB-C test board — a diagnostic tool that lets you probe individual electrical traces on the charging circuit without fully disassembling the phone. This saves time and prevents unnecessary teardown.

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What is a trace?On a circuit board, a "trace" is a thin copper pathway that carries electrical signals or power between components — think of it like a wire printed directly onto the board. When a trace is damaged or shorted, the circuit it belongs to stops working.

We ran diode readings across all the major charging-related traces.

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What is a diode reading?A diode reading (taken in multimeter diode mode) measures how much resistance a trace has in one direction. Normal readings fall within a predictable range. An abnormal reading — especially a reading of 0 (zero) — means the trace is  shorted: there's an unintended direct connection to ground, causing a fault.

Most traces came back normal. But when we probed the VBUS trace, we got a zero reading — a confirmed short.

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What is VBUS?VBUS is the main power input line on a USB-C connector. It carries the 5V (or higher, for fast charging) power from the charger into the phone. If VBUS is shorted to ground, the charger detects the fault and shuts off — which is exactly why the phone showed zero charging response.

Step 2: Teardown — Getting to the Motherboard

Soften the Adhesive

Place the phone on the REFOX RS30 ESD Repair Heat Mat set to 90°C for 1–2 minutes.

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Why use a heating mat instead of a heat gun?The REFOX RS30 Heating Pad delivers even, controlled heat across the entire back panel — softening the adhesive uniformly without hot spots. Its ESD (Electrostatic Discharge) protection is equally important: a single static discharge can silently destroy sensitive chips on the motherboard before you even open the device.

Remove the Back Cover

Use the REFOX RS70 PryPal Blade Kit to carefully slide between the frame and back cover and separate them. Work slowly around the perimeter — don't rush this step.

On the S23 Ultra, the back cover and wireless charging coil assembly are separate components. This is good news: you can lift the back cover cleanly without disturbing the wireless charging hardware.

Protect the Cameras

Before going any further, place a protective cover over the rear camera array. The S23 Ultra's camera lenses and sensors are extremely vulnerable to micro-scratches from tools or debris during disassembly. This is a step many technicians skip — and regret.

Disconnect Flex Cables and Remove the Motherboard

Use the REFOX RS75 Universal Knife Handle Set to carefully disconnect all flex cables.

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Flex Cable WarningA flex cable (flexible flat cable) is a thin, ribbon-like connector linking components like the screen, battery, and cameras to the motherboard. They are extremely delicate — always lift them straight up, never at an angle. A torn flex cable can add significant cost to the repair.

Once all cables are disconnected, the motherboard can be carefully lifted out.

Step 3: Confirm the Fault on the Motherboard

With the motherboard out, we referenced the REFOX Bitmap — our schematic reference that maps every trace and component location on the board — to locate the VBUS terminal on the FPC connector.

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What is a bitmap/schematic?A schematic is a diagram showing how all electrical components on a board are connected. The REFOX Bitmap overlays this onto a photo of the actual board, so technicians can find exact probe points without guesswork — critical when working on densely packed modern motherboards.

We probed the VBUS terminal. The reading was still abnormal — confirming the short was on the board itself, not in the charging port. The port was fine. The problem was deeper.

Next question: had the output circuit survived?

Step 4: Check the Output Circuit

The output circuit — the side of the charging path that delivers power to the battery and internals — sits underneath a metal shield on the back of the motherboard.

Why We Used a Grinding Pen Instead of a Heat Gun

Normally, technicians use a heat gun to remove shields. Here, we chose a precision grinding pen instead.

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Why avoid the heat gun here?Heat guns apply heat unevenly. The components packed under this shield are tiny and heat-sensitive. Uneven heating can cause cold joints or damage nearby chips — creating new faults while trying to diagnose the original one. A grinding pen removes the shield mechanically, with zero thermal risk to surrounding components.

We probed the output circuit — and got normal readings. The output side was intact. The fault was fully isolated to the input trace.

Step 5: Rule Out the Capacitor

A small capacitor near the VBUS trace could theoretically be causing interference. We isolated it, desoldered it, and re-tested the input trace.

Still shorted.

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What is Kapton tape?Kapton is a heat-resistant polyimide film tape widely used in electronics repair. It can withstand soldering temperatures without melting or leaving residue, making it ideal for isolating components during live testing or protecting nearby parts during rework.

With the capacitor eliminated as a variable, the conclusion was unavoidable: the fault was inside the motherboard's internal copper layers — not on the surface, not in any component. The trace itself, buried between laminated layers of the board, was shorted internally.

Step 6: The Hard Decision — Split the Board or Find Another Way?

Standard procedure for an internal trace fault is to split the motherboard — physically separate its bonded layers to access and repair the damaged trace. On older devices, this is manageable. On Samsung's S20 series and beyond, it's a different story.

Here's the problem:

  • Samsung uses large amounts of high-temperature solder paste in the middle bonding layer
  • Melting it requires sustained, prolonged heat — far longer than a typical reflow
  • That sustained heat causes CPU and UFS chip pseudo-soldering — joints that look intact but have actually weakened at a microscopic level
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What is pseudo-soldering (cold joint)?A pseudo-solder joint looks fine visually but has poor electrical contact. It can cause random crashes, boot failures, or data loss — often appearing days or weeks after the repair, making it extremely difficult to trace back to the board split.
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What is a UFS chip — and why does it matter?UFS (Universal Flash Storage) is the storage chip on modern Android phones — the equivalent of an SSD in a laptop. If the UFS chip is damaged or develops a cold joint during board splitting, all data on the phone can be lost permanently. There is no recovery from a failed UFS chip without specialized data recovery equipment.

Once the CPU or UFS is disturbed, the phone is classified as "heavily repaired" — and its resale value drops significantly. The risk-to-reward ratio of a board split on this device was simply too high.

So: was there another way?

Step 7: The Jumper Wire Solution

After a technical review, the REFOX team engineered a jumper wire bypass — routing power around the dead VBUS trace entirely, without touching the internal layers. 

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What is a jumper wire?In board-level repair, a jumper wire is a thin wire soldered between two points on a circuit board to bypass a broken or shorted trace. It's a well-established micro-soldering technique — essentially building a new road around a blocked one. The key is precision: the wire must be correctly routed, properly insulated, and mechanically secured.

The logic: since the VBUS input trace is dead, we run a new wire directly from the flex cable connector (where power enters from the charging port) to the output inductor (where power exits toward the rest of the board), bypassing the broken section entirely.

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What is an inductor?An inductor is a coil-based component that filters and regulates current flow. In charging circuits, it smooths out power delivery — preventing voltage spikes from reaching sensitive downstream components like the PMIC and battery.

Risks of the Jumper Wire Approach

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Know the trade-offs before proceedingThe jumper wire is fragile — a hard drop could break it. It's a non-standard repair that future technicians must be informed about. The phone's charging input path is now partially bypassed. Always disclose this fully to the customer and get their agreement before proceeding.

We informed the owner of all risks. He understood and agreed to proceed.

Step 8: Performing the Jumper Wire Repair

Remove the Bottom Speaker

Unscrew and remove the bottom speaker module to gain clear access to the work area on the motherboard.

Prepare the Output Inductor

Apply a controlled amount of flux to the output inductor.

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What is flux?Flux is a chemical agent that removes oxidation from metal surfaces and promotes solder flow. Without flux, solder beads up and creates cold, unreliable joints. In micro-soldering, using the right amount of flux is as important as the soldering technique itself.

Solder the Wire to the Inductor

Using 0.1mm enameled wire, carefully solder one end to the output inductor. This wire is approximately the width of a human hair — it demands a steady hand, proper magnification, and a fine-tipped soldering iron.

Clean and Insulate

  • Clean the solder joint with a flux-cleaning sponge
  • Apply UV solder mask (green oil) over the joint
  • Cure with a UV lamp
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What is UV solder mask (green oil)?UV solder mask is a liquid insulating coating that hardens under UV light. Once cured, it forms a tough, flexible shell over the solder joint — protecting it from vibration, moisture, and accidental shorts. Think of it as a custom-fitted insulating jacket for your repair.

This "insulation armor" locks the wire mechanically and prevents it from vibrating loose under normal use.

Prepare the Flex Cable Connector End

  • Gently scrape the coating off the target pad on the flex cable connector to expose bare copper
  • Apply medium-temperature solder paste
  • Add flux and solder the other end of the wire to this pad
  • Clean thoroughly with IPA or flux cleaner
  • Apply UV mask for insulation and cure under UV lamp

Verify with Multimeter

Probe the VBUS trace again. The readings should now be back to normal — and they were. The bypass was confirmed live.

Resolder the Capacitor

Solder the small capacitor back to its original position. Don't skip this — it plays a role in filtering the charging circuit.

Isolate the Original Faulty Input Pins

Apply a piece of high-temperature tape over the original VBUS input pins on the connector. This fully isolates the dead trace and ensures it cannot interfere with the new bypass path.

Step 9: Reassembly and Testing

Snap the flex cable connector back on — it should seat firmly with a clean click. Reassemble the motherboard and reconnect all flex cables in the reverse order of removal. Take your time here; a misaligned connector can introduce new faults.

Results:

  • ✅ Charging function: restored and working normally
  • ✅ OTG function (using USB-C as a power output to other devices): intact and working

Board Split vs. Jumper Wire: Which Is Right?


 Board Split Jumper Wire
Repair quality Permanent, factory-like Functional, non-standard
Risk to CPU/UFS High None
Resale value impact Significant Moderate
Skill required Extreme High
Best for Warranty / insurance repairs Customer-agreed value repairs

Conclusion

What looked like a simple charging fault turned out to be a lesson in one of the most important skills in professional repair: knowing when not to follow the textbook.

The standard answer — split the board — exists for good reason. It's the cleanest, most permanent fix. But on a Samsung S23 Ultra, the risks of that procedure are real and significant. A damaged CPU or UFS chip doesn't just cost money; it can mean permanent data loss for the customer. That's not a trade-off to make lightly.

The jumper wire solution we used here isn't a shortcut. It required precise diagnosis, careful schematic reading, steady micro-soldering, and proper insulation. It also required honesty — fully informing the customer of the trade-offs and getting their informed consent before proceeding.

At REFOX Lab, every repair decision starts with one question: what outcome is genuinely best for the device and the owner? In this case, a 0.1mm wire and a steady hand gave this S23 Ultra a second life — with the CPU and UFS chip untouched, and the customer fully in the loop.

🛠️ Tips & Tricks from the REFOX Lab Bench

These are the hard-won insights from this repair — the kind of knowledge that only comes from doing the work. Whether you're a seasoned technician or learning board-level repair, keep these principles close.

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Motherboard Split: The Risk Is Higher Than You Think Splitting Samsung S20 and later motherboards is one of the highest-risk procedures in modern smartphone repair. The CPU sits directly in the thermal path of the separation process — and unlike older boards, Samsung's use of large-volume high-temperature solder paste in the middle layer means you cannot rush the heat. Always use a calibrated hot plate with a thermocouple, monitor CPU temperature in real time if possible, and never exceed the safe thermal threshold. One degree too many, for one second too long, can silently destroy the CPU or cause UFS pseudo-soldering that won't show up until weeks after the repair.
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Grinding Strategy: Why We Choose the Pen Over the Heat Gun Samsung uses a transparent underfill compound beneath the shield that behaves differently from standard adhesive — it expands when heated, which can lift or crack nearby components if heat is applied unevenly. A heat gun, even at a controlled temperature, creates localized hot zones that accelerate this expansion unpredictably. A precision grinding pen removes the shield mechanically and gradually, with zero thermal input to the board. It takes longer, but it eliminates an entire category of heat-induced secondary damage. When in doubt: grind, don't heat.
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Transparency in Communication: The Most Important Repair Tool When a repair path could affect a device's resale value, long-term reliability, or data integrity, the conversation with the client matters more than the repair itself. Before proceeding with any non-standard solution — jumper wire, board split, chip replacement — make sure the client fully understands: what the repair involves, what the risks are, how it may affect resale value, and what happens if it doesn't work. A client who feels informed and respected will trust you regardless of the outcome. A client who feels surprised by a result — even a successful one — will not. Deep risk alignment before the repair is not optional. It is the repair.

What would you have done — full board split, or the jumper wire bypass? Drop your thoughts in the comments below, and watch the full repair on YouTube.

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