I have an old H.A. Armellin espresso machine that is leaking a little bit on the top of the boiler (See picture) it doesn’t matter how much I tighten it leaks a little bit of water on top of the boiler. Is there anything I can use to seal that?
Looks as if it could be seeping out around the electrode as in between the electrode shaft and the insulator that helps prevent this from happening. If that's the case the only likely fix is element replacement. Had that to happen on a FF X5 single boiler machine and tried a few different fixes, but nothing effectively sealed it.
With it in operation (be safe of course) did you see exactly where the water was originating from or just spotted that bit of a puddle? The way it looks it could've seeped out and just flowed downward. If it was just around the threads/nut then a possible fix like o-ring replacement and high temp RTV silicone would probably do it.