> I've seen this problem before with various CRTs - which is why I quickly =
narrowed in
> on the 'brightness knob'.  In short, I'm getting what some people used to=
 call
> 'blooming' in the vertical direction.  That is, the brighter the image at=
 that spot
> on the CRT, the 'taller' the image is.
> (not to be confused with 'defocusing' which also got called blooming)....=
 So I get
> way over-deflected leading and trailing edges - which quickly drops down =
to normal,
> just in time to overdeflect again on
> the trailing edge.   Of course this doesn't work very well with a scope
> which needs nice straight lines - I originally suspected the 10x scope ha=
d been
> misadjusted since it looked a lot like that, until I noticed lettering wa=
s doing
> weird stuff as well.
>=20
> What I don't remember is what causes this failure - i.e. if the crt is ju=
st bad and
> time to throw the scope away, or if it's likely just a bad
> capacitor/other component in some section of the unit.   Too many years
> ago for TV repair for me, and not really a lot of it when I did do it, so=
 it isn't
> coming back.

I would suspect a capacitor used in the inter-stage coupling to maintain HF=
 frequency response - or more correctly a resistor across such a capacitor =
going high resistance, or input resistor to the next stage going high resis=
tance. Either resistor going high could produce the over-compensated wavefo=
rm effect.
--=20
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--=20
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