Part VI — The Real Shop Toolkit · Chapter 22
Symptom-to-Fix Quick Tables
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Find the customer’s symptom in the left column. Do the first test first — it is the cheapest and most likely. Only move to the next cause if the test rules it out.
Smartphones
| Symptom | First test | Most likely causes (in order) | Fix / next step |
|---|---|---|---|
| Dead, no response | Known-good charger 15 min; force restart | Flat battery → faulty battery → charging port → board fault | Charge/replace battery; port; DC-supply diagnosis (Job Card 13) |
| Won’t charge | Clean port; known-good cable; USB meter | Lint → cable/charger → port/sub-board → charging IC | Job Card 1 → Job Card 5 → board repair |
| Charges slowly | USB meter shows low W | Charger/cable → port wear → battery health | Replace cable/charger; port; battery |
| Battery drains fast | Battery health; usage by app | Worn battery → rogue app → board leakage | Battery replacement; software check; DC-supply leakage test |
| Shuts down at 20–30% | Battery health | Worn battery | Battery replacement |
| Screen black, phone rings/vibrates | Flashlight test (LCD); display connector | Display damaged → connector → display power/backlight circuit | Test known-good screen → board repair |
| Lines/ink spots on screen | Visual | Damaged OLED | Screen replacement |
| Touch not working / ghost touch | Touch test; remove case/protector | Damaged digitiser → poor-quality screen → touch IC (older iPhones) | Screen replacement → board repair |
| No sound on calls | Speakerphone + headset | Blocked earpiece mesh → earpiece → audio IC | Clean → replace earpiece → board |
| Others can’t hear me | Voice memo test, each mic | Blocked mic hole → port flex mic → board | Clean → flex → board |
| Camera black/blurry | Each camera; check lens glass | Cracked lens cover → module → connector | Lens → module |
| No service / weak signal | SIM in another phone; SIM registration; APN | SIM/registration → antenna cable/flex → RF fault | Account/SIM → reconnect antenna → board |
| Wi-Fi/Bluetooth greyed out | Restart; reset network settings | Software → Wi-Fi module/board | Software → board repair |
| Overheating | Usage, charging state | Rogue app → failing battery → board short | Software → battery → DC-supply test |
| Restarts every few minutes (iPhone) | Panic log | Faulty peripheral flex → battery data → board | Chapter 15 panic flow |
| Stuck on logo / boot loop | Update via computer (iPhone); recovery/safe mode (Android) | Software → storage fault | Update/flash → board-level |
| Face ID/Touch ID not working | Settings messages | Damaged sensor/flex → non-genuine part → pairing | Genuine part + Repair Assistant or specialist |
| “Moisture detected” (Samsung) | Dry port; inspect | Moisture → corrosion → port | Dry/clean → port replacement |
| Liquid damage | Disconnect battery now | Corrosion | Chapter 16 procedure |
Laptops
| Symptom | First test | Most likely causes (in order) | Fix / next step |
|---|---|---|---|
| No power at all | Known-good charger; USB-C meter; battery disconnected test | Charger → DC jack/port → board fuse/input → short | Replace charger/jack → board diagnosis (Chapter 11) |
| Powers on, black screen | External monitor; flashlight test | RAM → panel/cable/backlight → board/BIOS | Reseat RAM → Job Card 10 → board |
| Runs on charger only | Battery report | Worn battery → battery connector → charge circuit | Battery replacement → board |
| “Plugged in, not charging” | BIOS/app charge threshold; wattage | Battery-care setting → wrong-wattage charger → battery/charger IC | Change setting → correct charger → battery |
| Overheating, loud fan, slow | HWiNFO temps | Dust/dried paste → fan → background load | Job Card 6 |
| Keys not working | On-screen keyboard works? | Liquid-damaged keyboard → ribbon → board connector | Job Card 11 |
| Touchpad raised/won’t click | Look at the case | Swollen battery | Battery replacement — safety first |
| Very slow | Drive type and health | HDD → low RAM → malware | Job Card 7, 8, 9 |
| Blue screens | Stop code; MemTest86+; S.M.A.R.T. | RAM → drive → drivers | Replace part / drivers |
| Wi-Fi missing | Device Manager | Driver → card/antenna | Driver → replace card |
| Hinge broken / lid separating | Visual | Broken hinge mounts | Lid replacement or hinge repair |
| Asks for BitLocker key | Microsoft account recovery key | Encryption triggered by BIOS/hardware change | Customer gets key at aka.ms/myrecoverykey |
Desktop PCs
| Symptom | First test | Most likely causes (in order) | Fix / next step |
|---|---|---|---|
| No power | Outlet, switch, PWR_SW short, +5 VSB | PSU → front-panel cable → board | Job Card 12 |
| Fans spin, no display | Debug LEDs/POST code; display cable | RAM → display output → CMOS/BIOS → CPU/board | Figure 7.1 no-POST order |
| Random restarts | Temps; stress test; Event Viewer | Overheating → PSU → RAM/XMP | Clean/repaste → PSU → disable XMP/RAM test |
| Beeps at start | Board manual beep table | RAM → GPU → CPU | As indicated |
| Shuts down when gaming | Combined stress test | PSU wattage/quality → GPU temps | Better PSU → GPU cooling |
| Not booting, “no boot device” | BIOS sees drive? Boot order | Boot order → SATA mode → drive failure | Fix settings → boot repair → replace drive |
| Slow | Drive health/type | HDD → malware → RAM | SSD, cleanup, RAM |
Copy these tables onto one laminated sheet per station. Before quoting any job, the technician points to the row and says out loud which test they will do first.
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