snip


Are the 330pF multilayer ceramic that could have metalisation creep /
cracks/ unreliable /leaky from humidity. I would replace them with a
different brand/construction



It would probably be worth doing some further checks on those caps to make
sure that they are not any part of the problem - if indeed there actually is
one. I'm not so sure now that I haven't somehow led myself up the garden
path, as I said elsewhere in the thread.

The actual type of cap is a high voltage pulse tolerant disc ceramic. I
think that these are single layer, aren't they ? Usually, if they do
anything, they get an arc track across them, and ultimately the plastic
coating splits. These are showing no signs of distress in any way. As to
changing them for a different type, I would consider that to be a big no. I
would never advocate using substitute parts anywhere in the primary side of
a switcher, particularly where high voltages and the magnetics are involved.
These things work by the skin of their teeth in the first place, and any
parts that I replace, are always sourced to be either dead ringers for the
originals wherever possible, or at worst, something of identical
construction and spec, from a different manufacturer.

Arfa