A few years back i bought a very cheap Motorola 4500x mobile phone. It weight around 4kg, and the analog phone network has been shut down long time ago.
Today i started to dismantle the phone. I want to replace its guts with a modern GSM module. Theres plenty of space, that's for sure.
- runs on 9v
- 12v battery pack, 4Ah, dead.
- undefined car charging connector , looks like a loop8 euro connector, but it is 12v and the plug is directional (positive pin is male)
- 1984 SMT components (!)
- replace handset pcb with atmega328 to handle UI and input.
- keep existing keypad and 10-digit led display
- remove the contents of the slave transponder module, replace with Efcom pro GSM module (i2c)
- use the curly wire to feed power, i2c and microphone/speaker wires
- use pwm to drive the ringtone/touch tone speaker.
I have already a working cell phone on a breakboard. Project sounds feasible!
A few pics to wet your apetite (i apologize in advance for the big images, i'm on a tablet here)