Is the top right corner of your glass very damaged? There is a sensor located there that detects whether or not the phone is against your face. This sensor, when active, will shut off the screen. It is likely this is the issue. If you carefully remove the cracked glass from the area you should get use of the screen back.
Once you are able to activate the LCD you can enter the diagnostic mode by pressing *#0* # . The sensor diagnostic test is the one that will tell you if the sensor is active or not. If the phone vibrates and the screen is green it means the sensor is active.
To answer your question on cost. The glass is available online for 8-10 dollars american. The first replacement will take someone skilled at least 1-2 hours because of the LOCA glue removal. I'm taking a guess you are from India - which puts your cost at around $75. Most shops here in the US charge around $50 so the quote does sound high.
In a pinch you can use a hair dryer. It just takes a really long time. Watch the temperature and DO NOT GO OVER 180 F. You'll need to periodically re-sweep the dryer on the glass to keep it warm as you pry off the glass from the LOCA glue.
Heat the whole thing up. Start from the top by the speaker for your ear. Use the spudger to get leverage between the glass and bezel. Add heat if there is too much resistance (the glue is at/neat it's melting temp so this doesn't take long). Work your way down with the heat gun as you get the glass to pry up.
Also, K and C are on the same scale... K is just based off absolute zero.
Matt - 70 - 80 C should be plenty fine. In fact, you're taking too long to heat the phone. All that is needed is to melt the LOCA glue that connects the LCD to the Glass and body. How you managed to get enough leverage to lift both LCD and glass is beyond me. Start at the top, heat the glass to 160 F (sorry got tired of converting from freedom units). You should be able to get between the glass and the bezel with the spudger. After that use the heat gun to progressively move down and you should see it separate rather easily. Cleaning it, though, is a different story. Buckle up.
If you attempt this be prepared to part ways with your phone. Controlling the heat is critical in not damaging the electronics. That said, if you have an oven thermometer you can make contact with the surface of the glass as you're heating it up to get an accurate gauge on the temperature. An IR thermometer is under $20 on Amazon (linked in the supplies of this teardown). It is an extremely useful tool to have around the house (also doubles as Cat laser pointer). Keep it under 180 degrees F.
Dude! good call. As long as you don't hold the thermometer in the hair drier/gun's heat you can easily save $20 by not buying the IR thermometer. That said, I really like my IR thermometer, very handy to have around the house if.
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Ecco un'anteprima di come il grafico apparirà:
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