I made the circuit as it is on the web. The thing is, that there was no reading of the ampmeter ( i have not reading of the ampmeter before ) when the power source came down, but the led wasn´t on when it happened. The load was a stepper motor of 1.4 amps per phase and 5 v, connected by a tanslator circuit of TIP120 transistors (that the have a protection diode), that were controlled via a circuit with the parallel port.(all conections were ok) I think that the problem has to be with Q1 as it is alreay on ,and i read a 45v betwen the colector and the emiter ,probably in the saturation region. I dont know if Q1 has burn out or just the negative rail is still at the the level of the shut down protecction circuit. Thanks for your support.