Start with the problem you can observe
- Complete phone diagnostic checklist before buying a used phone
Work through browser tools, native-app comparisons and the purchase checks that a website cannot verify.
- Phone speaker crackling or distorted
Compare sources, output routes and ordinary speech to narrow the cause before repeating tones.
- Dead pixel, stuck pixel or OLED burn-in?
Compare the size, background and persistence of a mark and document it for follow-up.
- Ghost touch on phone
Distinguish unwanted contacts from dead areas and repeat tests under controlled conditions.
- Phone microphone not working
Follow permission, input, recording and playback separately, then compare the app that fails.
Use observations without overstating them
These guides connect a specific symptom to a test and a useful comparison. They do not certify hardware, replace a repair inspection or promise a fix. Read the testing methodology for how the tools gather evidence, or return to the diagnostic hub to select an individual check.