Hacking Samsung SGH-E530 to kids phone
I have a old Samsung SGH-E530 phone which I wanted to convert to play phone. One worry about the phone was the ability to call emergency services (112, 911).
Flight mode was no option, since the phone had to be powered-down, which makes it quite useless as play phone.
Option number two involves drastic measures. Since I will not be needing any GSM capabilities any-more, let's take it out or at least the antenna bit.
Opening the phone was easy peasy, just remove 5 standard philips screws and good to go. Located the antenna, both internal and external and removed a few filter capacitors using tweezers to break them off the board. This will decouple the antenna.
Re-assembly and turning it back in, "Limited service 5 bars". A bit flaky though (holding the phone would make it drop a few bars) how-ever still stable enough to make calls.
Time for a revised plan, time to dive in again. Now locating the Power Amplifier Module (PAM), took the de-soldering station and removed the SKY77328-13 chip from the PCB.
Re-assembly and turning it back in, "Limited service 2 bars"!!! I am located 500 meters from a GSM tower (line of sight), so I am guessing this also helped the process.
Still more to be removed apparently. The "complete RF front end for multi-band GSM and GPRS wireless communications" SI4205-BM is the next canidate for heat-gun removal.
Re-assembly attempt number 3 and finally "No service available", guess I have hit the bulls-eye :-)
Bonus-challenge is setting the date or more precisely the year. The SGH-E530 will not accept the current year (2020), further inspection reveals the date must be set between 1-1-2020 and 31-12-2016. Either no engineer bothered to look this far in the future or a classical case of planned obsolescence.
I would like to set the date correctly to allow learning the day of the week kind of things. Every year the weekday to shift by 1 weekday (365 mod 7), except on a leap year, which is causing the weekday to shift by 2 weekdays.
I order to work around the date restriction I have to improvise. 1-1-2020 was a Wednesday, 6 years earlier, mind the leap-year 2016 in between, 1-1-2014 should be the solution. How-ever 2014 is not a leap-year unlike 2020, thus first of March 2014 is on a Saturday. 1st of March 2020 is located on on a Sunday.
Going back 6 more years to 2008 reveals an other interesting case. The leap-year criteria matches, how-ever located on Tuesday it's incorrect, since there are now 2 leap-years (2012 & 2018) involved.
Going back to 2003 gives me the correct weekday, how-ever no leap year. Going back to 1997, disqualifies as being no leap year. Next in line 1992. Jackpot, first of all a leap-year and secondly 1-1-1992 weekday is Wednesday.
My surprise grows since this behaviour (28 years) is consistent since 1-1-1964 is the next candidate in line. Which is even before UNIX Epoch Time, making it an unlikely candidate to even to be considered :-). I have tried to wrap my head around the math involved to explain it, how-ever I have to leave it "exercise left to the reader".
Back to my pressing matter of setting the right year allowing the weekdays to match has proven to be a rather difficult issue. I can only deal with it by using a work-around. Set the year to 2014 and at 1st of March change the year to 2015. Sounds like next level daylight saving time/summertime :-).