Unfortunately this seems to be a problem that happens to all sony ericsson z525a phones before too long. (And it seems sometimes it happens on the anniversary of the expiration of any and all warranties)
I do have some codes for running service tests on the sony z525 but with a blank screen they wont do you much good. anyway..
I'll post them here and let you know that when I tried them on my phone (when the screen worked) they did exactly what they were supposed to. You can test the screen...but only if the screen is working.
Unfortunately none of these codes will work if you have a phone with a blank screen...
To check the IMEI# = * # 06 #
Secret Service Menu= > * < < * < * (< is left, and > is right)
To reach last dialed numbers= 0 then #
Info about Simlock= < * * < (use with caution)
again...none of these seemed to fix the problem of the blank screen...but if you should get another z525a you can use these commands to do what they're listed to do....until the screen goes blank....
Now, to retrieve your numbers you would need to follow these key strokes...
center, toggle down (1 time), center, toggle up (2 times), center, toggle down (5 times), center, toggle down (5 times), center (3 times)
then wait for quite some time...it takes a while to copy all of the contacts...I would say anywhere from 5 to 10 mins...
this should work to save your contacts.
To save your pictures (and any other data you might want to retrieve) you could buy Sony's data cable
for the z525a. I haven't tried this but it should work since that is what the cable is for.
Its called a DCU-60 USB data cable, and is listed as being compatible with the z525a.
You could also try getting a T6 Torx bit screwdriver and taking it appart to replace the flex cable that runs to the screen...but I would suggest getting all the data off the phone first.