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A real-world inspection checklist — from someone who has bought, sold, and repaired hundreds of phones. Do these 10 checks before you hand over a single franc.
Buying a used Samsung phone in Switzerland can save you CHF 200 to CHF 600 compared to retail — but only if you know what you are doing at the point of sale.
Every week, people in Switzerland buy second-hand phones on Ricardo, Tutti, Anibis, and Facebook Marketplace. Some get a brilliant deal. Others walk away with a phone that has a cracked baseplate hiding under a case, a battery dying after two hours, or worse — a device still locked to someone else’s Google account.
I have personally bought, sold, and repaired hundreds of phones. The difference between a good deal and a disaster is almost always those first 15 minutes of inspection. This guide gives you the exact same checklist I run through every single time — step by step, nothing skipped.
- ✓ Physical condition & body
- ✓ Screen test — pixels, burn-in, and touch response
- ✓ Battery health & charging
- ✓ Samsung diagnostic code *#0*#
- ✓ Samsung Members full test
- ✓ Camera — all modes & video
- ✓ Speakers, mic & vibration
- ✓ IMEI & model verification
- ✓ Samsung & Google account lock
- ✓ Signs of repair or replaced parts
⚠️ BEFORE YOU MEET THE SELLER
In Switzerland, always meet in a public place a café, a train station, or a busy shopping centre. Never meet alone at someone’s home address to buy electronics. Ask for photos of the box, IMEI label, and receipt before you travel. If the seller is on Ricardo or Tutti, check their rating and how long their account has been active.
Physical Condition — Look First, Ask Questions Later
Before turning the phone on, do a full physical check
The moment the seller hands you the phone, resist the urge to switch it on immediately. First, do a slow, deliberate physical inspection from every angle. This takes 90 seconds and can reveal a lot about how the phone was treated — and whether parts have been replaced.
- ✓ Screen glass: Hold at an angle under light — look for micro-cracks, deep scratches, or faint hairlines near the edges that are easy to miss head-on.
- ✓ Frame & corners: Dents on the frame or bent corners are a sign the phone was dropped hard. Internal damage from falls is often invisible until it becomes a problem later.
- ✓ Back glass or cover: Check for cracks, chips, or discolouration. On Samsung A-series, the back is plastic — on S-series it is glass. Any cracking means the phone absorbed a serious impact.
- ✓ Camera lenses: Look directly at the lens glass on the back. Scratches on the camera lens directly reduce photo quality — this is often not mentioned by sellers.
- ✓ Charging port (USB-C): Shine a light inside — look for bent pins, corrosion, or lint packed inside. A damaged port is a painful repair.
- ✓ All physical buttons: Press each one — volume up, volume down, power/side button. They should click cleanly with no stiffness or rattle.
- ✓ Remove any case or screen protector: Always do this. A case can hide scratches, cracks, or even a bent frame. A screen protector can hide a cracked display underneath. If the seller refuses to remove it — walk away.
💡 PRO TIP
On Samsung Galaxy S and Note series, the frame is metal. Run your finger along the side and feel for any ridge or bulge — this can indicate a swollen battery underneath pushing outward. A swollen battery is dangerous and must be replaced immediately.
Screen Test — Pixels, Burn-in, Green Line & Touch
Samsung AMOLED screens can develop specific problems — know what to look for
Samsung uses AMOLED displays on most Galaxy phones, especially the S and A series. These screens are excellent but they have specific failure modes you need to test for. A screen replacement on a Samsung S23 or S24 can cost CHF 150–280 — more than enough reason to inspect carefully.
The fastest way to test the screen is Samsung’s built-in diagnostic code. Open the phone dialer and type:
SCREEN TEST CODE
Open the Samsung phone dialer and enter this code:
*#0*#
Then tap RED, then GREEN, then BLUE. Check the screen carefully for dead pixels, green lines, burn-in marks, shadows, or any uneven colour patches.
Each colour fills the whole screen. Any dead pixels, stuck pixels, or dark patches will show up clearly against a solid colour.
- ✓ Dead pixels: Small black or coloured dots that never change. Check all three solid colour screens.
- ✓ Burn-in: Faint ghost images from a previous screen — most commonly a keyboard, status bar, or navigation bar permanently visible. Tilt the phone slightly to see it. Very common on older Samsung models used at high brightness.
- ✓ Green line defect: A vertical green line running from top to bottom of the screen is a known hardware fault on some Samsung Galaxy models, including some S21 models. It can appear after a drop or flex stress. This is not fixable without a full screen replacement.
-
✓
Touch response: In the same
*#0*#menu, tap Touch and draw lines and circles across the entire screen. Every area should respond — especially near edges and corners. - ✓ Brightness range: Crank brightness to max, then to minimum. AMOLED screens at minimum brightness should go nearly completely dark.
- ✓ Auto-brightness & proximity sensor: Cover the top sensor with your finger — the screen should dim or the call interface should appear during a call.
🚨 WARNING
If you see a green line on the screen, do not let the seller convince you it is “just a small issue.” A vertical green line means the display needs full replacement. This is usually a CHF 150–250 repair. Either negotiate the price down by that amount or walk away.
Not Sure What to Do
With Your Phone?
I Can Help.
The Fix Mission is currently run by me personally. With 5 years of experience in phone repair, buying, and selling, I offer free advice before you buy a used phone, sell your current device, or pay for a repair. My goal is simple: help you make a safer decision before spending money.
Get Free Advice →Battery Health & Charging Test
A degraded battery will ruin a good phone — always check this
The battery is the component most likely to fail in a used phone. Samsung does not display a battery percentage like Apple does, but you can check the real battery condition using a combination of built-in tools and a quick physical check.
Check battery status via secret code:
BATTERY TEST CODE
On some Samsung Galaxy models, you can open the phone dialer and enter this code:
*#0228#
This can show battery voltage, temperature, and ADC reading. If the battery temperature is unusually high, the voltage looks unstable, or the phone heats up quickly during normal use, treat it as a warning sign before buying.
A healthy battery at full charge shows around 4.35–4.40V. A reading significantly lower at “100%” charge suggests the battery can no longer hold a full charge.
Also check via Settings:
BATTERY USAGE CHECK
To check battery usage on a Samsung Galaxy phone, go to:
Settings → Battery and Device Care → Battery → Battery usage
- ✓ Physical swelling check: Place the phone on a flat table and try to spin it gently. If it spins easily or one side lifts, the battery may be swollen and pushing the back cover out.
- ✓ Fast charging test: Plug in a USB-C charger and watch. After 30 seconds, the screen should show a “Fast charging” or “Super Fast Charging” notification if the port and battery are healthy.
- ✓ Wireless charging: If the Samsung S-series or A-series model supports wireless charging, test this too. A phone that charges wired but not wirelessly often has a damaged charging coil — another repair cost.
- ✓ Battery temperature: After 5 minutes of use, the phone should not feel hot — warm is fine. Excessive heat suggests battery degradation or a background process problem.
Samsung’s Secret Diagnostic Code — The Buyer’s Best Friend
One hidden code tests almost every hardware component in seconds
This is the single most powerful tool you have when inspecting a used Samsung — and almost no ordinary buyer knows about it. Samsung Galaxy phones have a hidden engineering diagnostic menu that was built for technicians but works perfectly for buyers too. You do not need to install any app. Just open the dialer and type:
- ✓ RED / GREEN / BLUE: Tests full-screen colour display — check for dead pixels, patches, or discolouration.
- ✓ Speaker: Plays a test tone through the bottom speaker — listen for crackling or distortion.
- ✓ Receiver: Tests the earpiece — it should produce clear, undistorted audio.
- ✓ Vibration: The motor should vibrate strongly and evenly — a weak or noisy vibration motor is a sign of wear.
- ✓ Camera: Opens the camera in diagnostic mode — check all lenses.
- ✓ Sensor: Tests proximity, accelerometer, and gyroscope — important if the phone was ever dropped or repaired.
- ✓ Touch: Draw patterns across the whole screen, including all four edges and corners.
- ✓ Sub Key: Tests the hardware buttons — press each one when prompted.
💡 PRO TIP
On newer One UI versions, including One UI 6 and above, this code may be restricted on some carrier-locked models sold in Switzerland. If the code does not open a menu, use the Samsung Members app instead. On unlocked models and most Ricardo/Tutti phones sold in Switzerland, *#0*# usually works properly.
Samsung Members App — Full Diagnostic Test
The official Samsung diagnostic tool — thorough and easy to use
The Samsung Members app is Samsung’s official diagnostic tool and it tests every major hardware component with a single tap. It is pre-installed on most Samsung phones — if it is not there, it can be downloaded from the Play Store in under a minute.
SAMSUNG MEMBERS DIAGNOSTIC TEST
If the hidden code does not work, open the Samsung Members app and go to:
Samsung Members App → Support → Phone Diagnostics → Test All
This test checks important hardware functions like battery, screen, touch, speakers, microphone, sensors, vibration, camera, and charging. If any test fails, use it as a warning sign before buying.
The “Test All” scan covers: NFC, Bluetooth, Wi-Fi, camera, microphone, speakers, USB-C cable charging, touchscreen, fingerprint sensor, heart rate (if applicable), and more. Some tests require you to interact — press buttons, listen to audio, or touch the screen in a specific area.
- ✓ Run the full “Test All” scan: Let it complete every test without skipping. This gives you a quick overview of the phone’s main hardware condition.
- ✓ Watch for any “Failed” results: Even one failed component should be discussed with the seller before paying. It may mean repair cost later.
- ✓ Fingerprint sensor test: Register your own fingerprint temporarily and test it. Most buyers skip this, but it only takes around 30 seconds.
- ✓ Wi-Fi and Bluetooth: Both should connect instantly. A phone that struggles to find networks or keeps dropping connections may have a hardware antenna issue.
📋 NOTE
You do not need to be logged in to Samsung Members to run diagnostics. You can use it as a guest. If the seller has their account logged in, that is fine — the diagnostic results are the same.
“The five minutes you spend on a proper camera and diagnostic test will save you far more than the two hours you will spend trying to get a refund later.”
Camera Test — Every Lens, Every Mode
Do not just take one photo. Test all modes separately.
Camera repairs on Samsung phones are among the most expensive. A replacement camera module for a Galaxy S24 Ultra can cost CHF 120–200. Test every lens individually — sellers sometimes only show you the main lens because it is the one that still works.
- ✓ Main (1x) lens: Take a photo indoors and outdoors. Look for sharpness, correct exposure, and no focus hunting.
- ✓ Ultra-wide (0.6x): Tap the 0.6x icon and take a photo. Check for dark corners, vignetting, or blurry edges which may indicate lens damage.
- ✓ Telephoto zoom (3x / 5x / 10x): On models with multiple zoom levels, test each one. A blurry or shaky telephoto image can be a sign that the optical zoom module is damaged.
- ✓ Portrait mode: Shoot a portrait with background blur. The bokeh should be smooth and even — patchy or glitchy blur may suggest a sensor calibration issue.
- ✓ Night mode: If you are meeting indoors or in low light, test Night mode. It reveals how well the sensor and stabilisation are working.
- ✓ Front camera (selfie): Switch to the selfie camera. Take a photo and check focus, brightness, and any distortion around the edges.
⚡ QUICK VIDEO + MIC TEST
Switch to Video mode and record 20 seconds. Talk normally while recording. Then play it back with full volume. You are checking: video stabilisation, autofocus smoothness, and whether the microphone picks up your voice clearly without muffling, static, or echo. This single test covers both camera and mic at the same time.
Speaker, Microphone & Vibration Test
A blown speaker is a hidden cost many buyers discover too late
Samsung Galaxy phones from the S series and many A-series models have stereo speakers — a bottom speaker and an earpiece that doubles as a second speaker. Both should work clearly. A damaged speaker is not just annoying — it is expensive to replace.
- ✓ Bottom speaker test: Play a YouTube video or music at full volume. Listen carefully for crackling, buzzing, or distortion — this is the most common speaker failure and is often caused by drops or water ingress.
-
✓
Earpiece test: Use the
*#0*#Receiver test, or make a short call. The voice should be clear with no buzzing through the top earpiece. - ✓ Stereo balance: In landscape mode, play music with both speakers. The left and right channels should be balanced at a similar volume.
-
✓
Microphone test: Use the
*#0283#audio loopback code. Speak into the mic and it should play back immediately. Test the bottom mic RCV_1stMic and top mic SPK_2ndMic separately. -
✓
Vibration motor: In the
*#0*#menu, tap Vibration. A healthy motor gives a strong, clean buzz. A weak rattle or irregular vibration means the motor is worn.
💡 PRO TIP
Also test with the Voice Memos / Voice Recorder app. Samsung phones have 2–3 microphones. Recording with the native app uses a different microphone path than video, so it will catch problems that the video test misses.
IMEI Check & Model Verification
Never skip this. A stolen phone can become worthless overnight.
The IMEI (International Mobile Equipment Identity) is the fingerprint of your phone. Every mobile network in Switzerland can blacklist a phone by its IMEI if it is reported stolen — which means the phone will stop working on any Swiss network. A stolen phone sold on Ricardo today could stop working tomorrow.
Find the IMEI three ways:
IMEI QUICK CHECK
Open the phone dialer and enter:
*#06#
This shows the IMEI instantly on the screen. Compare this number with the IMEI on the original box, receipt, and phone settings. If the numbers do not match, do not buy the phone.
IMEI SETTINGS CHECK
Settings → About Phone → IMEI Information
SIM TRAY IMEI CHECK
Another place to check the IMEI is the SIM tray:
SIM tray → IMEI is usually engraved on the tray or printed inside
- ✓ Match to the box: The IMEI printed on the box label must exactly match the IMEI shown on the phone. If they are different, the phone may have been swapped out.
- ✓ Check on imei.info: Enter the IMEI at imei.info. It can show the real model number, storage, colour, and country of sale. If the seller says it is a Galaxy S24 256GB but the IMEI shows 128GB, you are being misled.
- ✓ Check Samsung warranty: For Samsung, check warranty status through Samsung’s own support/warranty portal or by using imei.info. This helps you see whether the phone may still be under warranty.
- ✓ Verify model number: In Settings → About Phone, the exact model number, for example SM-S928B, should match Samsung’s official Swiss or European model variant.
🚨 SWITZERLAND-SPECIFIC WARNING
In Switzerland, Swisscom, Sunrise, and Salt all participate in the national IMEI blacklist. A phone reported stolen to any Swiss operator can be blocked on Swiss mobile networks. Never buy a used phone without verifying its IMEI not even from someone you know.
Google Account Lock & Samsung Account Check
A locked phone is a brick. Confirm both accounts are removed before paying.
Android phones have a security feature called Factory Reset Protection (FRP). If the phone is factory-reset while a Google account is still logged in, it will ask for that Google account’s password after restart and no one else can unlock it. This makes stolen phones unsellable — but scammers still try to sell them.
Check Google Account (FRP):
ACCOUNT LOCK CHECK
Settings → Accounts and Backup → Manage Accounts
No Google accounts should be listed. If there is one, ask the seller to remove it in front of you right now — not later, not after you pay.
Check Samsung Account:
SAMSUNG ACCOUNT CHECK
To check if a Samsung account is still connected, go to the top of the Settings page:
Settings → Samsung Account
The Samsung Account should also be signed out. Samsung’s Find My Mobile feature works similarly to Google’s FRP — an active Samsung Account can lock or remotely wipe the device.
- ✓ Factory reset the phone yourself: The best way to avoid account lock is to factory reset the phone in front of the seller, set it up from scratch, and confirm it does not ask for any previous Google or Samsung account credentials.
- ✓ Do not transfer: Refuse the deal if the seller says, “I will send you the email and password later.” This is a common scam — accounts can be recovered later and the device may be remotely locked after payment.
- ✓ Knox security check: Samsung phones use Knox hardware security. Check Settings → About Phone → Knox Version. If Knox shows 0x0, it is clean. A modified Knox flag, for example 0x1, means the bootloader may have been unlocked and the phone was potentially rooted.
🚨 NEVER PAY BEFORE ACCOUNTS ARE REMOVED
This is the single most important rule when buying any used Android phone. We have seen many cases in Switzerland where buyers paid, received the phone, and within 24 hours the phone was remotely wiped and locked via Find My Mobile. Once the money has changed hands, it can be very difficult to recover it.
Signs of Previous Repair or Replaced Parts
Repaired phones are not always bad — but you deserve to know
A repaired phone is not necessarily a problem — screen replacements and battery swaps are completely normal. What matters is whether the repair was done properly with quality parts, and whether the seller has disclosed it. Here is how to spot repair history that was never mentioned.
- ✓ Adhesive residue on edges: Samsung phones are sealed with adhesive. If you see messy glue residue or uneven adhesive around the screen or back panel, it has been opened and resealed. This is not always a problem, but it should have been disclosed by the seller.
- ✓ Uneven gaps: Run your finger around the edge of the screen and back glass. If one section sits slightly higher or lower than the rest, it may have been replaced and not fitted properly.
- ✓ Screen colour inconsistency: Compare the white tone of the screen at low brightness with another Samsung phone of the same model if possible. A non-genuine replacement screen may look slightly more blue or yellow than the original.
- ✓ Mismatched screws: If any screws are visible, check if they look stripped, scratched, or mismatched. This is often a sign of previous disassembly or careless repair work.
-
✓
Knox check for root/unlock: Use
*#0*#and also check Settings → About Phone. A tripped Knox counter, such as 0x1 or higher, means the bootloader was unlocked, usually for rooting. This can void Samsung warranty and disable secure features like Samsung Pay.
💡 FROM MY REPAIR EXPERIENCE
A screen replaced by a proper repair shop using a genuine Samsung panel is perfectly fine and should not affect your decision — as long as the price reflects it. What you want to avoid is a screen replaced with a cheap aftermarket panel that fades, loses sensitivity, or develops green lines within a year. If in doubt, ask for the repair receipt.
BEFORE YOU PAY
Price Negotiation — Use What You Found
Every defect you find is a legitimate reason to negotiate
After your inspection, you will likely find one or two things that are not perfect. Use them. Sellers on Ricardo and Tutti almost always leave room in their price, and a confident, specific negotiation based on real issues is completely normal in Switzerland.
- ✓ Battery below 80%: A battery replacement at a reputable repair shop in Switzerland costs around CHF 60–90. Deduct that from the asking price.
- ✓ Screen scratches or burn-in: Minor cosmetic scratches can justify CHF 20–40 off. Actual burn-in or a green line should mean full screen replacement cost deduction — around CHF 100–250, depending on the model.
- ✓ No original box or receipt: This is a legitimate reason to ask for CHF 20–30 off, especially if IMEI verification is harder.
- ✓ Non-genuine or aftermarket replacement part found: Negotiate based on the cost to replace that part with a genuine Samsung part.
- ✓ Missing accessories: No original charger, cable, or earphones can add up. CHF 10–20 per missing item is a reasonable deduction.
Not Sure What to Do
With Your Phone?
I Can Help.
The Fix Mission is currently run by me personally. With 5 years of experience in phone repair, buying, and selling, I offer free advice before you buy a used phone, sell your current device, or pay for a repair. My goal is simple: help you make a safer decision before spending money.
Get Free Advice →✅ Final Checklist Before Payment
Screenshot this and take it with you
Physical Condition
No hidden cracks, frame intact, camera lens clear
Screen Test Passed
No dead pixels, no burn-in, no green line, full touch
Battery Healthy
Charges fast, no swelling, no excessive heat
*#0*# Diagnostic Passed
All tests green — display, speaker, touch, sensor
Samsung Members Passed
Full diagnostic test — no failed components
All Cameras Working
Main, ultra-wide, zoom, selfie, video + mic
Speakers & Mic Clear
No crackling, both speakers balanced
IMEI Verified
Matches box, clean record, correct model
Google Account Removed
No FRP lock risk — no accounts linked
Samsung Account Removed
Find My Mobile disabled, Knox clean
good
Amazing info. Very helpful
Very information Thanks
Thank you for very detailed article and very useful tips. I just have one follow up question about the fake or non original phones in the market. Sometimes, it is hard to differentiate the fake ones as they look really close to the original ones. Any tips?
Very well explained and all technical analysis along with pros and cons were clarify specifically
This is apt. As a Samsung fan, this is helpful