Don't get me wrong, I've had a number of personal organisers, one of my favourites being the Psion 5, plus a Campaq PDA with GSM - although I mostly used the latter for playing Sodoku until the stylus got lost.
So I got my I9100 and for a few weeks it was fantastic. I then decided to install the RF Signal Tracker app to determine whether I could use it as an alternate way of running GSM field tests. However, Android 2.3.3 and 2.3.4 on the I9100 has a bug with the callback for GSM signal level changes, thus the app gets stuck on the same receive signal level indefinitely. I know this worked in 2.2 so I tried to roll back.
Unfortunately whilst flashing the phone back to 2.2 the process stalled and didn't complete such that I had to disconnect the phone and reboot. I tried to get back into the bootloader download mode using the Vulcan death grip (Vol Down + Home + Power) but nothing... black screen. Then it dawned on me I'd bricked the phone and no combination of keys would make it power on! It was pretty clear I'd lost the bootloader and it was never going to power on again.
A bit of googling suggested a USB adapter with a 300kR resistor between pins 3 & 4 on the USB may work, but I didn't have a spare micro USB plug or lead, so I couldn't try it anyway - although I suspect it wouldn't have helped. The final trick is to disconnect the battery, connect the USB cable, then reinsert the battery, which also did nothing.
I'm currently in a part of the world where the only hope of repair is to send the phone off to the UK or the US for repair. I therefore decided to purchase a JTAG debugger so I could rewrite the bootloader myself, which would work out about the same cost as sending away, if not cheaper.
I opted for the RIFF JTAG box. It arrived in a couple of weeks and today I had a go at repairing the phone.
First up I installed the JTAG Manager software and downloaded the resurrector DLL files for the Samsung I9100, including downloading the latest JTAG Manager and unit firmware.
Next I made up the breakout cable by soldering the ribbon cable with the IDC connector on one end to the breakout PCB supplied. A bit fiddly, but not too difficult.
Then I was ready to solder jumper wires from the JTAG breakout PCB to the phone itself...
The I9100 comes apart fairly easily by removing the rear cover, battery, the 7 visible screws, then gently prying apart the plastic starting from the sides and top, then hinging out the bottom.
Then I saw the size of the jtag solder pads and their proximity to each other!!! I could barely see the pads, never mind trying to solder to them! There's no way the average person would be able to solder wires to these pads, the non-solder press-on jig is the only realistic option.
An even bigger problem was that I only had available a large 25W Antex soldering iron, some fairly large diameter solid core wire and the Mk.1 eyeball.
Unperturbed I had a bash at soldering the wires on anyway. Very very fiddly! However, with a bit of luck I managed to tack on all the wires and gingerly slipped in the battery. Hit start on the programmer and it wrote about 60% and failed - damn! Tried again and the update completed successfully! Result!
Re-assembled the phone, slipped in the battery and up she came.
I am now a legend amongst my work colleagues for my ninja soldering skills. That was certainly the most difficult soldering job I've ever attempted.
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