Samsung Galaxy S9+ (SM-G965F) will not turn on or charge: step-by-step diagnostics
Step-by-step diagnostics: from the simplest (cable, charger) to measurements on the board. Each step says what to do, where to measure and what to do with the result. Go in order: most phones “come back to life” at steps 1–3.
What you need
| What | Why |
|---|---|
| another USB-C cable and charger (preferably an original Samsung 9 V) | rule out the simplest cause |
| a USB tester (plugs in between the charger and the cable) | see whether current flows into the phone, without opening it |
| a multimeter with thin probes | measure the battery voltage and on board components |
| a bench power supply (0–5 V, current limit) | steps 3 and 5: “wake up” the battery, check the board |
| a heater / hot air, a suction cup, plastic picks | remove the back glass (it is glued) |
| a PH000 Phillips screwdriver, tweezers, a magnifier | screws, connectors, inspecting the board |
Safety. A swollen battery — do not charge, heat or “wake” it: replacement only. Before soldering and working with connectors — disconnect the battery. When measuring on a powered board, do not short neighbouring parts with the probe: they are smaller than a millimetre here.
Step 1. Without opening the phone (5–60 minutes)
- Another cable and another charger.
- Inspect the USB-C port with a flashlight. Carefully clean out dirt and lint with a wooden toothpick (you can wet it with isopropyl alcohol). Do not poke metal into the port.
- Leave it on charge for 30–60 minutes, even if the phone “stays silent”: a deeply discharged battery first charges with a small current, and the screen shows nothing during that time.
- Hold Power + Volume down for 15–20 seconds — a forced restart.
- If you have a USB tester, look at the current:
| The tester shows | What it means | Where next |
|---|---|---|
| 0 mA | power does not reach the board | cable / port → step 4 |
| 50–150 mA, steady | a very flat battery is slowly charging | wait an hour, then step 3 |
| 0.5–1.5 A | the phone charges normally | the problem is in powering on → step 6 |
| jumps 0 ↔ 100 mA | the phone tries to start and restarts | step 3, then step 7 |
Came back to life — stop here. Did not — we open it.
Step 2. Disassembly
The back glass is glued on. The order from the Samsung manual:
- Heat the phone to 70 °C for 10–20 minutes (a dryer, a hot plate or hot air around the edge).
- Lift the glass with a suction cup and run a pick around the edge. Careful on the left — the fingerprint sensor flex is there: disconnect its connector first.
- Remove the 16 screws and take out the SIM tray.
- Remove the upper and lower plastic covers (by the holes on the sides).
- Remove the board screw, disconnect the battery connector, the two coaxial cables and the other connectors (8 places — red frames in the photo of step 7).
- Disconnect the sub board connector (SUB PBA — the USB-C port is on it).
While the board is out — inspect it under a magnifier: green deposits, corrosion, traces of water near the connectors (especially at the bottom, near USB). Water is the most common cause of exactly this combination of “does not charge + does not turn on”.
Step 3. The battery
Multimeter in DC volts, probes on the battery connector contacts (battery disconnected from the board).
| Voltage | What to do |
|---|---|
| above 3.8 V | the battery is fine → step 4 (charging) or step 5 (power on) |
| 3.0–3.8 V | connect it, put it on charge, check again |
| below 3.0 V | the manual says: replace the battery. You can try to “wake it up” (below) |
| 0 V | the battery protection has tripped or the battery is dead → “wake it up” or replace |
How to “wake up” a battery (only one that is not swollen and worked recently): bench supply at 4.0 V, 0.2–0.3 A limit, on the battery contacts observing polarity, for 3–5 minutes. The voltage rose above 3.3 V → put it back into the phone and on a normal charger. It does not rise or the battery gets warm → replace it.
Step 4. Why it does not charge
The manual’s “8-4-6-1 Cable Charging” algorithm: measure in turn from the USB connector to the battery. The board is assembled (battery and sub board connected), the charger is plugged in. Multimeter minus on a metal shield or the board frame (that is “ground”), plus on the test point.
| Step | Where to measure | Normal | If it is not normal |
|---|---|---|---|
| A | C8070 (voltage from USB, VBUS_IF_5P0) | 5 V or 9 V | replace the SUB PBA sub board (with the USB port) or its flex |
| B | C8069 (after the input protection, CHG_IN_5P0) | 5 V or 9 V | replace the input protection chip (see the note) |
| C | is the battery charging? (USB tester: the current rises) | yes | replace the charger chip U7006 |
Note. The algorithm was written for the S9 (G960F) and at step B says to replace U8007. The S9+ (G965F) board has no U8007 — neither on the layout drawing nor in the parts list. Next to C8069/C8070 sits U14007 — most likely the input protection on the S9+, but without the G965F schematic this is not confirmed. C8070, C8069 and U7006 do exist on the G965F.
Step 5. Current from a bench supply: is the board alive
Disconnect the battery. Bench supply: 4.0 V, 1–2 A limit, on the battery connector contacts on the board (observing polarity). Watch the supply’s ammeter:
| What we see | What it means | What to do |
|---|---|---|
| high current straight away, before the button | a short circuit on the battery line | find the hot part (finger, rosin smoke, thermal camera) and remove it |
| 0 mA, and still 0 when pressing Power | start-up does not begin | step 6 — the button |
| 50–200 mA on pressing, then drops to 0 | start-up began and broke off | step 7 — U7011, inductors, crystal |
| rises to 300 mA or more, holds, “jumps” | the board is booting | step 8 — the display |
Step 6. The power button — R3004
The manual: “Check the voltage level at R3004 while pressing power key. Is the voltage high?” Battery (or bench supply) connected, minus to ground, plus to R3004. Measure with the button pressed and released: the voltage must change noticeably.
| Result | What to do |
|---|---|
| no voltage / does not change with the button | replace the power key flex (Power key FPCB); check its connector |
| the voltage is high, the button works | step 7 |
Step 7. Power management chip U7011, inductors and crystal
The button works but the phone does not start — check the voltages produced by the power management chip U7011. Measure on the inductors (output side, relative to ground) at the moment you press the power button.
| Inductor | Where relative to U7011 | Normal, at least |
|---|---|---|
| L7003 | top row, first from the left | 0.75 V |
| L7011 | top row, second from the left | 1.1 V |
| L7008 | top row, right of the large L7014 | 1.1 V |
| L7009 | top row, far right | 0.6 V |
| L7013 | right, below L7009 | 2.0 V |
| L7022 | right of U7011, below L7023 | 0.75 V |
| L7004 | bottom right | 0.75 V |
| L7012 | bottom right corner | 1.3 V |
| L7024 | left, the upper large one | 0.75 V |
| L7000 | left, below L7024 | 0.75 V |
| L7006 | below U7011, the small left one | 0.75 V |
| L7010 | below U7011, the small right one | 0.85 V |
The manual’s tolerance is ±10 %. The voltages appear only for a moment after pressing: if the multimeter cannot keep up, an oscilloscope is better.
| Result | What to do |
|---|---|
| one or more voltages missing or below normal | first check that the line is not shorted (inductor resistance to ground); no short — replace U7011 |
| all voltages are fine, the phone does not start | crystal OSC7000: oscilloscope, 20 µs/div, there must be a stable signal; none — replace OSC7000 and U7011 |
Two clarifications to the manual. (1) The “AP_PS_HOLD = 1.8 V” step could not be shown on the board: it is a signal name, not a part, and the layout drawings do not show it — the G965F schematic is needed. (2) The manual gives the crystal frequency as “32.768 MHz”. An oscilloscope setting of 20 µs/div corresponds to a frequency in kilohertz — this is an ordinary 32.768 kHz clock crystal; “MHz” is most likely a typo.
Step 8. Sound or vibration, but the screen stays black
If on power-up there is vibration or sound, the phone warms up or the computer sees it — the board is alive and the problem is the display (the manual: “Change the FRONT-LCD ASSY”). Check: connect another display or make sure the display connector is seated firmly.
Summary: symptom → what to replace
| Symptom / reading | Most likely |
|---|---|
| battery below 3.0 V and will not “wake up” | the battery |
| no 5/9 V on C8070 | the SUB PBA sub board (USB port) or its flex |
| present on C8070, missing on C8069 | input protection (U8007 per the S9 manual; on the S9+ most likely U14007) |
| present on C8069, the battery does not charge | U7006 (charger chip) |
| high current from the bench supply without the button | a short circuit: find the hot part |
| R3004 does not react to the button | the power key flex |
| no voltages on inductors L70xx | U7011 |
| voltages present, the crystal does not oscillate | OSC7000 + U7011 |
| vibration/sound present, no picture | the display |
Manual files (Samsung service manual)
- G960F_repair_algorithms_and_service_schematics.pdf · 1602 KB — repair algorithms: p. 4 “Power On”, p. 9 “Cable Charging”, p. 10 “Wireless Charging” (written for the G960F; part numbering matches the G965F except U8007)
- G965F_mainboard_components_side1.pdf · 1643 KB — component layout, side 1 — U7011, OSC7000, inductors L70xx
- G965F_mainboard_components_side2.pdf · 1242 KB — component layout, side 2 — C8070, C8069, U7006, R3004
- G965F_disassembly_and_assembly.pdf · 2442 KB — disassembly and assembly — pp. 4–7
- G965F_parts_list.pdf · 267 KB — parts list — Samsung part numbers
- G965F_service_manual_general.pdf · 476 KB — general part of the manual
The text in the PDFs is tiny: to find a part, press Ctrl+F and type its number (e.g. R3004) — the viewer will highlight it on the drawing. The pictures in this guide were made from these files.
Article changelog
| Date | What changed |
|---|---|
| 2026-11-04 | Guide written: 8 steps, pictures from the manual, manual files. |
| 2026-11-05 | Published on the blog without changes to the content; English version added. |