>>44897
If you have access to similar inexpensive device you should test it with that.
How long the light illuminated? Or is it constantly working?
I've seen a led bulb very slowly going dark after switching it off (not sure how long it took tho).
>in some tubes
If you are lucky. Sometimes they just smear the plaster over the wiring.
>it is complex task to open it (and also pretty destructive).
It is.

I can ask a pal, but first if you could answer the questions above, it would be nice.