On Sunday 27 April 2008 21:04, Wiebe Cazemier wrote:

On Sunday 27 April 2008 20:52, James Sweet wrote:

Don't be so quick to condemn the CRT, sure it could be at fault, but
eliminate the external stuff first! A bad connection on the neck board can
just as easily cause the same symptom.

But won't a bad connection give me a black screen, because when the cathode
is disconnected from it's line, no current can flow. How can the blue cathode
be shorted to ground on the neck board? I can't see anything (obvious) on the
board that could cause a short.

BTW, I thought the RGB guns had separate line wires, but besides the focus
and grid voltage wires, only one extra thick wire runs to the neck board.
That has to be the cathode line voltage, right? And if so, doesn't that mean
that when it's shorted to ground, all the guns are fully turned on, and not
just the blue one (as is the case here)?

Wait, I've been thinking. An intermittent short in a capacitor between the blue
cathode line voltage and ground could of course also cause this (and there are
some of them, ceramics, on the neck board). But one question about that, which
I guess also applies to when the short is inside the CRT:

Provided there is one cathode driving voltage for all guns, why aren't all guns
fully turned on when one of the cathodes is shorted to ground? Because if one
is shorted to ground, there is no more line voltage for the other guns either,
right?