S
Smarty
Excellent !!!!
Excellent !!!!
I've been trying to reason this through. The best I can come up with
is this...
Whether purity is good or bad, the electron beams have to land
/somewhere/. In a B&W image, it might not matter much if red winds up
on blue, blue on green, and green on red. The result will be
/something/ approximating a shade of gray.
Correct, as I explain elsewhere in the thread
Arfa
As a newcomer to this group, I hesitate to be a contrarian
or appear to be in any way argumentative or disagreeable.
What most likely happened here is that that the solder connections to the degaussing thermistor went bad and opened up on the initial surge after turnon.
The idea is to magnetise one way and the other at less and less strength, evenually decaying to zero. What hapens in this failure mode is it gets magnetised one way, the connection breaks and the process is incomplete.
Because of the high amperage involved there is usually a brown ring around the connection. To resolder you have to remove the old solder and clean the pin as well as the pad.
The other possibility is the shadow mask (aperature grill in a Sony) cut loose.
in message
You didn't hesitate to do it to me. Don't pretend to be "diffident,
modest, and shy", because you aren't.
technical mumbo-jumbo, particularly when it arises from
ignorance, arrogance, or a combination of the two.
Thank you all. I've read all the posts as of last night, and I also
like the idea of degaussing and of using a magnet to see what happens.
"Smarty" wrote in messagenews:koj00iuvh1@dont-email.me...
You didn't hesitate to do it to me. Don't pretend to be "diffident, modest,
and shy", because you aren't.
I don't have as much experience servicing TVs as others in this group. But I
have noticed that impurity is less visible with a monochrome signal than a
color one. Clearly, the visibility will vary with all the factors stated,and
possibly some we've missed.
I can understand your confusion about this point, and it is a point of
confusion I share. But I must remind you of what Sherlock Holmes said, that to
speculate without data weakens the mind.
To argue about what is or is not theoretically visible is a complete waste of
time, when a simple experiment would resolve the issue. (And if anyone reading
this thinks I will slide the yoke on my 13" Trinitron to see what happens--
they are mistaken.)
"Smarty"
** The set is a 19 inch Sony - so it is a Trinitron type.
I suspect the behaviour is typical of Triniton with a magnetised aperture
grille. The degaussing thermistor may have failed in the set and at the
instant of failure left with a parting blow by magnetising the grille.
The OP can check for this by noting if the usual switch on " bong" noise
still happens.
He can also bring a magnet near ( not touching) the screen and see if that
tends to fix various areas.
Your chosen example that the 3 guns are mis-registered uniformly, andThere is purity, which is making sure the
3 beams hit their respective phosphors.
Let us assume that for some reason, all three electron guns come in at
an incorrect angle thru the shadow mask or grid or screen. The blue
electron gun hits 50% on the blue phosphor and 25% on the red and 25%
on the green phosphor. The red gun hits 50% on the red phosphor and
25% on the blue and 25% on the green phosphor. The green gun hits 50%
on the green phosphor and 25% on the red and blue phosphors. All
three phosphors are illuminated at 100%, so only differing electron
beam strengths due to compensating for differing phosphor efficiencies
will be noticeable in any color shading of white and gray areas of the
picture.
As to questioning the credentials of the people that have replied to this,
being new, you should probably be aware that the William has a lifetime's
experience at the sharp end of service, sales and technical writing, Bob
has lectured the stuff, I spent many thousands of hours of my life working
on this stuff at nuts and bolts level, and Phil, for all his occasional
rants and outbursts, is a highly qualified service engineer whose
technical understanding and ability is without question.
found a power supply for it, and right now I also can't remember where"The only degaussing coil I have came from a tv I destroyed. I never
aperture grill is still in the right place."But I don't think there was an earthquake**, so I'm figuring the
similar design) or possibly a bulk tape eraser.
A bulk eraser will work, but make sure you don't accidentally shut it offnear
the set. I caused serious harm to a Trinitron when this occurred.
That is 100% correct, and an adept description of how such errors are
barely noticeable on a black and white picture. Understand also that
we are talking pure CRT physics here. Don't get confused by colour
signal weightings that are part of the encoding and transmission
process. Whilst there are some differences in the efficiencies of the
phosphors, and the eye is non linear in its response to the visible
spectrum, those differences are not huge, and for white through shades
of grey, the three beam currents will not be wildly different for a
CRT that's in good emmissive order. Hence the reason that mass beam
landing errors are not anything like as important to the reproduction
of an accurate grey, as you might imagine. The fact that such errors
are much easier to see on a colour picture may well be a perceptual
one, as the human eye / brain combination, is extremely good at
handling colour perception. Single beam landing errors - convergence
errors - are of course, much easier to see on a black and white picture.
As to questioning the credentials of the people that have replied to
this, being new, you should probably be aware that the William has a
lifetime's experience at the sharp end of service, sales and technical
writing, Bob has lectured the stuff, I spent many thousands of hours
of my life working on this stuff at nuts and bolts level, and Phil,
for all his occasional rants and outbursts, is a highly qualified
service engineer whose technical understanding and ability is without
question.