I'm new here and fairly new to android too but have a rough understanding as I would see it compared to most of you.
I have 2 phones here that I have acquired cheaply due to issues (not questionable backgrounds) and done extensive research here and across the net on each of their problems but come to no real conclusions with either one.
Phone 1: Galaxy S2 16gb GT-I9100
Phone operates perfectly... as a mini wifi tablet. Doesn't seem to recognize any kind of SIM I put into it, just gets no signal at all. Baseband, IMEI, IMEI SV, IP Address, etc are all unknown. Signal says 0dBm 99 asu. As far as I can tell from what I have read this is an EFS file problem.
I have tried swapping EFS file with one from another S2 I have, start up with a jig, new rom flashing x2, and have recently got a program call EFS Professional 2.0.70 but have no idea how to use it. I believe you can write an efs file but needs to be in Linux? I have also been told this is most likely a motherboard problem. What is the way to fix this myself if possible or possibly with someones assistance if you feel generous?
Phone 2: Galaxy S3 4G 16gb GT-I9305
One day the phone restarted itself and without showing any boot screen just showed a white screen with coloured dots shaded through it. This screen also happens when attempting recovery mode. I can access download mode. Phone appears in Odin.
I have tried try to flash official samsung release 4.1.2 BLL3 rom I get the error message that: 'There is no PIT partition'.
When flashing just cwm recovery or a kernal with no rom I get the same message. When trying to flash m3xx_i9305.pit I get: 'Get pit for mapping' and it just hangs on that. is this something that would take hours to do or is it just frozen? I also have PIT magic but not too sure how to mess around with that... Should I just get the text readout of the pit file from another i9305 and compare the 2 to make sure it's right? I have been told this will need a JTAG repair but then others have had success. The only thing I haven't been able to try yet is flashing a pit file with the rom as a 3 part file.
A repairer has told me that the S2 EFS problem is a maybe fix and could be the motherboard so not to get my hopes up and has also told me the the PIT problem is a fried flash chip and isn't really fixable.
Another offers JTAG for $60 and a $45 refund if it doesn't work and also an EFS repair service but is on holidays for another month.
Any help or advice would be greatly appreciated but I have researched this to the best of my ability so please only comment if you really know what you are talking about and have encountered (and fixed) either of these problems.