  CeRhSn with the Ce atoms forming a quasikagome lattice in the hexagonal plane
has recently been discussed in the context of quantum criticality driven by
magnetic frustration. Furthermore, it has been reported that the successive
substitution of Rh by Pd leads to magnetic order. Here we have investigated the
change of the 4$f$ occupation in the substitution series CeRh$_{1-x}$Pd$_x$Sn
for for $x$ = 0, 0.1, 0.3, 0.5, 0.75 by means of photoelectron spectroscopy
with hard x-rays (HAXPES). The quantitative analysis of the core level spectra
with a combined full multiplet and configuration interaction analysis shows a
smooth decrease of the 4$f^0$ contribution with rising $x$ due to an increase
of the effective 4$f$ binding energy $\varepsilon_{4f}$ and the reduction of
the effective hybridization $V_\text{eff}$. We further compare valence band
data with the calculated partial density of states and find that the Pd 4$d$
states are about 1eV further away from the Ce 4$f$ states at the Fermi energy
than the Rh 4$d$ states. In fact, the effective binding energy
$\varepsilon_{4f}$ of the 4$f$ states in the configuration interaction analysis
of the core level spectra decreases by the same amount.
