  It is shown, that the saturated $\alpha$-effect taken from the nonlinear
dynamo equations for the thin disk can still produce exponentially growing
magnetic field in the case, when this field does not feed back on the $\alpha$.
For negative dynamo number (stationary regime) stability is defined by the
structure of the spectra of the linear problem for the positive dynamo numbers.
Stability condition for the oscillatory solution (positive dynamo number) is
also obtained and related to the phase shift of the original magnetic field,
which produced saturated $\alpha$ and magnetic field in the kinematic regime.
Results can be used for explanation of the similar effect observed in the shell
models simulations as well in the 3D dynamo models in the plane layer and
sphere.
