frank wrote in
:

Jorgen Lund-Nielsen wrote:


However it seems to me that this kind of fault could be due to a bad
CRT,

The effect is independent of the sweep rate?

yes, totally independent of sweep rate. Track bending is always at the
same position and of the same entity.

I would expect a hard mechanical hit has loosen or bended a deflection
plate,
that often shows such effects and they are then sweeptime independent.

That's also my guess, but as I said, I'm not at
all an expert of scopes and CRT.
Maybe not a deflection plate as for more than half screen the track
looks absolutely perfect?


Could it be a problem caused by too high
EHT for a long time?

Not trace geometry problems.
too much beam current can burn the phosphor and create a dark spot or line.
and raising the EHT voltage shrinks the display size and then your gain
adjusts don't have enough range.

Deflection plates are pretty hard to bend.It's more likely that the glass
rods that hold the plates in position are broken or cracked,or a mesh
expansion lens has had it's screen distorted or torn.I don't know if your
CRT has the mesh lens,though.(they result in a less focused or more fuzzy
beam spot.)


--
Jim Yanik
jyanik
at
kua.net