Alternator strap problems

I have an Astra 1.7 TD of 98 bought a few months ago and does not stop leaving the alternator's strap, they have told me that it can be from the pulley but I have already changed the entire alternator and remains the same.
I need help.
thank you

When changing the alternator's strap, it also combines changing the tensioner of the belt, because, the old belt is always more weaned than the new one and when you replace it, like the tensor dock does not have so much strength to tighten the belt, the tensioner fails times. I recommend changing the tensor and try it, have if the noise is silent.

Thanks for answering, but my belt did not squeak. The problem is that it breaks, starting with the teeth of the inner face.
Tell you that my belt is trapezoidal.
all the best

This problem is because the belt is not original. I start 4 since the distribution changed and speaking with another mechanic I am spplician that is due to the angle of the V of the belt that does not settle well in the pulleys