[Hardware Hacking General] PepaLogik:
Memory transfer report

Hi all,

So my phone's memory transfer has been realized and I am going to report on it as I find it rather fascinating and it might be helpful for someone.

First a summary of previous facts. My Siemens A31 got wet and shut down earlier than I removed the battery. I did not have the right screwdriver, so I could not dry the insides for a few days. Then there was corrosion, of course. This was cleaned successively by alcohol, ultrasound and heating. Nothing helped, the phone was still dead. It only seemingly recharged the battery while the charger was connected, but nothing was shown on the display, no light, no sound, no possibility to power the phone on.

I was trying to find someone who would solder the memory chip into another phone for a reasonable price. A specialized company would probably do this job for about 2000 CZK (about 75 EUR). However, a guy in a laptop service told me that even if the memory was functioning and the soldering would be done right, the phone would get blocked due to an IMEI mismatch (as I have already reported and asked about here). Since no one seemed to know whether this was the case for such an old cell phone, I decided to go on.

Through friends, I found a guy who would do the soldering for 500 CZK (20 EUR). So I started to look for a functioning A31 phone. While making the rounds of cell phone second-hand shops, I encountered an office of a data recovery company. Although they do not focus on cell phones, I was curios to ask about it. The man there told me that the way I was going to recover my data was impossible, but he did not want to or could not say why. So I went on.

I eventually got a functioning A31 for 400 CZK (15 EUR). As I brought it home, I dismantled it and found that the ICs were different! The memory chip identification differed completely, while that of the CPU just slightly. I could find only the datasheet of my original memory, not of the "new" one, nor of the CPUs, so it was not clear whether these ICs were cross-compatible. The motherboards looked the same (except for the serial numbers and the like). As we could not figure out whether it was compatible, the only possibility was just to try it.

So that kind guy unsoldered both memory chips and soldered the one (hopefully) holding my data onto the functioning motherboard. After cooling, I put the pieces together and tried to turn it on - nothing. It was dead like the old phone. So I dismantled it and he heated the chip again, while trying to place it more finely. Assembled again, turned on and - what? It powered on! The SIM card was not there, so the phone was only telling me to insert it, but I could see that the color scheme was correct. When I powered it on with the SIM card inserted, it registered in the network normally and downloaded new text messages. As the most important thing, all of my data are there! Contacts, messages, reminders and notes, everything is back! I am really happy with it. There is even the message that was received while I was walking in the downpour, that killed the phone. Yeah, that message was still unread :). And the IMEI - guess what. I have my original IMEI again :cool:.

To summarize it, I have both my data back and a fully functioning cell phone for 900 CZK (approx. 33 EUR or 45 USD).

So what about the conclusions.

BGA soldering is not trivial - the chip must be placed very precisely. Although that guy is very experienced in electronics, this was his first BGA soldering (hence the low price).

Do not believe everyone who claims that something is impossible. On the other hand, the happy end of my story does not guarantee that this method will always work. It only demonstrates that it may work, at least for older phones.

Back up regularly. ;)

Good luck,

Jan