Hey Kvakva, thanks for doing the tests. My voltage drop is much higher. When i put a load of 1.5A the voltage drops nearly to 0V. I did what audioguru suggested concerning the voltage in the output of U1. I have a steady voltage of 11V, even under load conditions. I'm almost giving up this project, i measured everything that i thought could cause the problem and i found nothing that seems to be wrong. Kvakva, can you tell me what were the modifications that you did in the original project? What transistors did you use for Q1 and Q3? The only thing that i can't understand is the voltage between base and emitter of Q2 and Q4. I measure none voltage drop. I believe i should be measuring 0,7V but i can find the problem. Can you measure also these voltages on your ckt? Thanks for helping me Kvakva and congratulations for your success!!!!! Is this the project that you build?