Abstract
By using the Faddeev equations, a local, central, perturbing potential and a small mass difference between the particles are introduced into Amado's three-body model. It is shown that to first order in the perturbing potential and in the mass difference, an equation of the same form as Amado's equation will result. The additional terms which appear in the kernel are obtained explicitly. An expression is obtained for the shift in energy of a three-body bound-state pole, in terms of the shift in the kernel. It is shown that the contribution of the perturbing potential to the energy shift is just the expectation value of the potential.