I'm having problem getting any output from this universal adapter for my older laptop, so I opened it up to see this rubber-like white substance inside, on top of the big 68uF 400V capacitor.
A closeup:
If it is glue, why would they use it? It fits well without it, with the leads of that capacitor bent as they are.
A lot of times you'll use glue/epoxy to protect against a mechanical shock (i.e. dropping it). Put it on the at-risk items, like the biggest capacitor, and you have more anchor points with less stress on the solder joints.
Generally this is a silicone elastomer which as mentioned helps to keep large components in place or closely spaced components from touching.
