"Wiebe Cazemier" wrote in message
b.home.nl...
I tried the tapping a bit more, and now the red gun also has this
problem... I
didn't tap that hard I think (from the description "not enough to break
it,
but close" I would think I need to tap a lot harder).

Now my question is: are those cathodes/filaments so fragile that I could
have
damaged them, or is it possible I dislodged dirt which now also affects
the
red gun?

The filaments were cold BTW, when I tried this. I suppose warm filaments
are
more easily damaged.

They could be that fragile, it depends, obviously one of them was fragile
enough to short in the first place. Now that you have two guns with issues,
there's no sense trying to isolate the heater because the guns would just
short to each other.