translate a field inside the collection with entity translation, not the collection itself

Is there a way to translate a textfield inside a collection, without changing the collection itself?

I have a node with a repeatable field collection-field. This collection consists of an imagefield and a textfield. The translator-role should only be able to translate the textfield inside the collection, not the (repeatable) field collection.

I have tried several ways, nothing worked for me.

As a workaround, I replaced the textfield with a nodereference to a "boilerplate"-/template-node which is translateable.

thanks tobias