fix

src/scippnexus/nxdata.py

@@ -486,16 +486,9 @@ def __init__(self, attrs: dict[str, Any], children: dict[str, Field | Group]):
             attrs=attrs,
             children=children,
             fallback_dims=('time',),
-            fallback_signal_name='value',
+            fallback_signal_name='value' if 'value' in children else 'time',
         )
 
-    def _init_signal(self, *args, children, **kwargs):
-        super()._init_signal(*args, children=children, **kwargs)
-        if self._signal is None:
-            if 'time' in children:
-                self._signal_name = 'time'
-                self._signal = children['time']
-
     def read_children(self, sel: ScippIndex) -> sc.DataGroup:
         # Sublogs have distinct time axes (with a different length). Must disable
         # positional indexing.