  We study del Pezzo surfaces of degree 1 of the form w^2 = z^3 + Ax^6 + By^6
in the weighted projective space P_k(1,1,2,3), where k is a perfect field of
characteristic not 2 or 3 and A,B \in k^*. Over a number field, we exhibit an
infinite family of (minimal) counterexamples to weak approximation amongst
these surfaces, via a Brauer-Manin obstruction.
