The Microsoft Lumia 640 LTE is a Windows smartphone developed by Microsoft. This was released on March 2, 2015, identified by model number RM-1073.
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Phone vibrates as it’s turning on, but will not turn on.
Try powering on the device while the phone is charging. If the phone does not turn on, the problem may be the charger. Try using the charger on another phone. If the phone does not charge, you will need to purchase a new charger. You can replace the charger by purchasing it directly from Microsoft or the iFixit store.
Plug your Lumia into a computer or wall adapter to charge. If the device is not charging from these two options, the phone has a dead battery. What you need to do here is replace the battery with a new or used battery, and test to see if the phone will turn on. If again it does not work, then there is a hardware problem with the power button or the circuit boards. If the phone turns on, plug the charger into the wall or computer and see if the charging icon appears. If the icon appears, then no further troubleshooting is necessary.
It is possible that it looks like nothing is happening because the display is bad. This may be caused by damage in the LED display. If so, you may need to replace the display.
The device is unresponsive, frozen or a blue screen occurs. These signs indicate a hard reset is needed.
Phone will not charge or will not remain powered on without being plugged into charging source.
Remove the rear cover of your phone to expose the battery by simply prying off the cover. Remove the old battery and replace with an original Nokia battery: BT-T5C
Try powering on the device while the phone is plugged in. If the phone does not turn on, the problem may be the charger. Try using the charger on another phone. If the phone does not charge, you will need to purchase a new charger. You can replace the charger by purchasing it directly from Microsoft or the iFixit store.
Sound is not clear coming through the phone. This could be a cause by a blockage of the sound system on the phone.
This problem may be due to playing compressed sounds such as Youtube videos or low-bitrate MP3 files. Change 400 frequency in your equalizer to nullified level so that this frequency no longer plays.
Make sure that all system apps are updated to the current version. To do this go to store, …, settings, check for updates.
Make sure speakers are clear of debris on the outside. If any dirt or other foreign substance is in the speakers, the speaker may crackle or distort any sounds produced by the speaker.
If your phone screen freezes or touch screen fails to respond.
If the device is unresponsive, frozen or a blue screen occurs, this indicates a hard reset is needed.
With the device turned off, hold the Power button until the device vibrates, then release. Then press and hold the Volume Down button and release it when an exclamation mark comes up on the screen. Enter the following button combination: Volume Up, Volume Down, Power, Volume Down to perform a hard reset. The device will reset and boot automatically. This may take a few minutes.
Phone has trouble getting a good connection.
Remove the sim card from your phone and test it in another working phone. If your sim card does not work in the other phone, then you may have a damaged sim card. If you have another sim card, plug it into your Microsoft Lumia 640 LTE. If the issue persists, the problem is the device, not the sim card.
If you are in a spot where service is bad, move to a different location and see if the wireless connection improves. If the connection improves, it may be your wireless provider. If the connection does not improve, see below.
If your phone has a screen protector or any kind of tape or protective film, it could be causing a blockage in the wireless connection.
