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Ok so recently i changed my m4 aqua display(bought from ebay) It started on.When i was unlocking my phone the display switched off but touchscreen still working, Its not a sowtware problem because i reinstalled fresh copy of android trough pc companion. Later i installed same old display and still the same problem. Sound touch vibration working but display not showing… i read that it may be a backlight problem that it stopped working or something.

Hi! It sounds like you may have blown out your backlight circuit. Is there a very faint image visible if you clean the glass really good and shine a bright flashlight on it at an angle? If so, then that’s a bad backlight. Cheers! If you found this information to be useful, please Up Vote or Accept Answer

@chappylv could be a filter (fuse) but before you go ahead and look for somebody who can do the microsoldering part for you, replace the display assembly. At least that way you can either rule it out, or rule in it, as the culprit. One of the main issue is going to be the unavailability of Sony schematics. Sony has stopped even making schematics which will make it difficult to trace components for failure. Here is the trouble shooting sequence from Sony: Check: Check whether the phone vibrates after the on/off key has been pressed. Action: If the activation described above is not detected, refer to section 1.1 ‘Power’. Check: Check the connection between Display FPC and Main PBA. Action:

  1. If not properly connected – disconnect and reconnect.
  2. If dirty or oxidized – clean the connectors. Check: Replace the Main PBA with a known working one and test the Front Cover Assy. Action:
  3. If the Front Cover Assy is still not working – replace it. Run Touch Panel Calibration after replacing Front Cover Assy according to 1297-3232!
  4. Replace Main PBA. 1.6.1 Illumination Check: Inspect external port of Light Sensor on the Front Cover Assy.

Action: If dirty – clean it. Check: Inspect the Light Sensor on the Main PBA.

Action:

  1. If dirty – clean it.
  2. Replace Main PBA. No, you do not have to necessarily replace the PCB. There are ways to create new backlight ways if it is a component on the board etc. Let us know what you find.