Hi! So far two GSM Arduino Shields get on fire in my house.
The first one, on september. The system has worked since June a lot of time always with usb power. I connected it to a wall power adaptor (12V-0,5A) and the system doesn't work properly and it smell just a bit like something was burning. As I was doing a demostration and I was sure the system is working, I plug it to another power adaptor (12-2A) and it it came on fire at the same moment of connecting. In despite of designers of GSM shield, this time I must say I'm not sure to have connected a circuit well enough because I've connected the circuit without verifying twice or three times before connecting.
The second Arduino shield burned last week. This time I'm completey sure that everything of my part was ok. The system was working properly attached on a computer for usb power supply. I decided to test it with a battery and I simply disconnected the usb and, with the barrel connector (power on center, ground surrounding), I gave power from a Yuasa SW280 12 V battery and it was on fire and the same moment of connecting. I know that's unbelievable but these two arduinos burned when I was showing my system at the same person. What I said to him? "I don't understand, I don't know what could happen, I'm very disappointed.."
In both cases, maybe a information important for those pretending to reproduce the situation: the fire comes at the same moment of connecting.
This week I've received new Arduino GSM shield (I've spend money on them) but I confess I'm very afraid to connect it and I've not done so far. This time I see there is a diode in paralel to the capacitor that always explodes. The worse is to think if the system remains alone with nobody in the surroundings and we can have a big fire.
My wife said not to try to let this devices connected if I'm not with them.
That's life, (very disappointing with scenes like these)