I have some variables which are scale but their limits vary. Namely, the one has range from 1 to 30, the other from 2 to 5, and so on.
Is there any way to tranform them (or recompute them) in such a way that they will be standardised and will all have the same range?
I agree that z-scores could be useful here. Go Analyze > Descriptive Statistics > Descriptives, then select whichever variables you want, choose some kind of descriptive statistic of interest to allow the dialog to run, and tick the "Save standardized values as variables" box.