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Why do old trinitron tubes go green?

H

h

Jan 1, 1970
0
As per subject. My other old CRTs go dim but all the trinitron ones go
green. Is there a simple explanation?

Cheers,

h
 
D

Dave Plowman (News)

Jan 1, 1970
0
As per subject. My other old CRTs go dim but all the trinitron ones go
green. Is there a simple explanation?

It's not just Trintrons - pretty well all decent CRTs do this. At one time
to get a pure red the phosphor used was less sensitive than the others, so
that gun was driven the hardest. So aged first - resulting in the green
tint.

Later CRTs used a more 'orange' red which was more efficient and didn't
exhibit this fault. But wasn't as good as the original when new.
 
E

EDM

Jan 1, 1970
0
Dave Plowman (News) said:
It's not just Trintrons - pretty well all decent CRTs do this. At one time
to get a pure red the phosphor used was less sensitive than the others, so
that gun was driven the hardest. So aged first - resulting in the green
tint.

Later CRTs used a more 'orange' red which was more efficient and didn't
exhibit this fault. But wasn't as good as the original when new.

That's for sure. Anyone remember Zenith's FTM1490?
Just stunning red.
 
D

Dave Plowman (News)

Jan 1, 1970
0
That's for sure. Anyone remember Zenith's FTM1490?
Just stunning red.

Yes. First generation PAL sets in the UK - dating from about '70 - were
capable of superb pictures when properly set up. Then the rot set in with
PIL tubes. They may have been consistent, but never as good as a decent
shadowmask.

I work in TV production, and think the grade 1 monitors used for camera
setup use the same NTSC phosphors as all those years ago...
 
I

ian field

Jan 1, 1970
0
Dave Plowman (News) said:
Yes. First generation PAL sets in the UK - dating from about '70 - were
capable of superb pictures when properly set up. Then the rot set in with
PIL tubes. They may have been consistent, but never as good as a decent
shadowmask.

I work in TV production, and think the grade 1 monitors used for camera
setup use the same NTSC phosphors as all those years ago...

--
*Very funny Scotty, now beam down my clothes.

Dave Plowman [email protected] London SW
To e-mail, change noise into sound.

It sounds like you're speaking of the shadowmask in the past tense as if
modern CRTs don't use them anymore!

The 70s tubes were delta gun types and as I remember them, the convergence
(both static and dynamic) was downright evil to set up correctly. The PIL
tubes only need static convergence (if that!) and don't get mis aligned as
easily as the old delta gun tubes did, almost every delta gun set I ever
serviced needed convergence adjustment whilst this need became extremely
rare with the later PIL tubes.
 
J

Jamie

Jan 1, 1970
0
h said:
As per subject. My other old CRTs go dim but all the trinitron ones go
green. Is there a simple explanation?

Cheers,

h
green does the least work.
 
M

mc

Jan 1, 1970
0
green does the least work.

Hmmm...

Trinitron is a single-gun tube. I would expect it to go dim rather than
having a color shift. If it goes green, maybe by losing the ability to
deflect the electron beam from stripe to stripe?
 
mc said:
Hmmm...

Trinitron is a single-gun tube. I would expect it to go dim rather than
having a color shift. If it goes green, maybe by losing the ability to
deflect the electron beam from stripe to stripe?

1 gun in terms of G1,G2 but 3 separate cathodes that do indeed age at
different rates. I spotted a Sony PVM1354 at work today that is going
green and will need a new bottle shortly. Another common age symptom is
is highlight clipping of a single color, often red. It resembles a
'puddle' of the bad color. Only cure is to replace the tube.

GG
 
H

h

Jan 1, 1970
0
Cool, thanks for the answers. Always wondered, seems obvious when you hear
the explanation.

Cheers,

h
 
J

James Sweet

Jan 1, 1970
0
Dave said:
It's not just Trintrons - pretty well all decent CRTs do this. At one time
to get a pure red the phosphor used was less sensitive than the others, so
that gun was driven the hardest. So aged first - resulting in the green
tint.

Later CRTs used a more 'orange' red which was more efficient and didn't
exhibit this fault. But wasn't as good as the original when new.


They haven't used the old fluorgermanate red phosphor in decades, early
60's or so? I've never actually seen a CRT that used it, everything in
my lifetime has been the newer orangish vanadate phosphor.
 
J

James Sweet

Jan 1, 1970
0
h said:
As per subject. My other old CRTs go dim but all the trinitron ones go
green. Is there a simple explanation?

Cheers,

h


The green phosphor tends to be the most efficient, if you've ever seen a
green fluorescent tube you'll see what I mean, the green is about 2x as
bright as the blue and many times brighter than the red.
 
D

Dave Plowman (News)

Jan 1, 1970
0
They haven't used the old fluorgermanate red phosphor in decades, early
60's or so? I've never actually seen a CRT that used it, everything in
my lifetime has been the newer orangish vanadate phosphor.

Grade 1 monitors used to setup the pictures from broadcast cameras use a
much more 'red' phosphor than TV sets. Decent computer monitors for
graphics too. I dunno what it is, but they don't generally go so 'bright'
as domestic ones.
 
I

ian field

Jan 1, 1970
0
James Sweet said:
The green phosphor tends to be the most efficient, if you've ever seen a
green fluorescent tube you'll see what I mean, the green is about 2x as
bright as the blue and many times brighter than the red.

Either that or the human eye is most sensitive at the green wavelength.
 
J

James Sweet

Jan 1, 1970
0
ian said:
Either that or the human eye is most sensitive at the green wavelength.

It is, that's the other part of the equation, but the lumen rating is
substantially higher for the green than even for white.
 
I

ian field

Jan 1, 1970
0
James Sweet said:
It is, that's the other part of the equation, but the lumen rating is
substantially higher for the green than even for white.

Next you're going to tell us how green is brighter than white - which is
made up of red, green & blue......................
 
J

James Sweet

Jan 1, 1970
0
Next you're going to tell us how green is brighter than white - which is
made up of red, green & blue......................


Depends, if it's a modern trichromatic fluorescent tube then yes, it's
made up of red, green and blue phosphors mixed as appropriate to obtain
the desired color temperature however the red and blue phosphors are
less efficient than the green so the white tube does indeed produce
fewer lumens than a green one. If it's one of the older halphosphate
phosphors (CW, WW, CWX, WWX, D) then it's a single color phosphor and
the emission is much more broad though with an abundance of yellow at
least in the case of CW and WW.

Personally I like the 80 series trichromatic tubes, 850 is a nice cool
5000K white with 80+ CRI, 835 is a more neutral 3500K which is a bit
more pleasant for living spaces. CWX is a standard halphosphate with the
addition of a fluorogermanate phosphor which emits a true deep red which
pushes the CRI up to around 90 but the light looks a bit pink to me.
There's some other nice mixes out there but many are hard to find.
 
P

Paul Hovnanian P.E.

Jan 1, 1970
0
ian said:
Either that or the human eye is most sensitive at the green wavelength.

Or there's something about the color modulation that, with aging
components, causes the signal to drift toward green. I have an LCD (3"
screen) color TV that is about 10 years old. When driven from a
composite video input (from a DVD player) it looks fine. But the
broadcast signals are starting to look a bit green.
 
I

ian field

Jan 1, 1970
0
Paul Hovnanian P.E. said:
Or there's something about the color modulation that, with aging
components, causes the signal to drift toward green. I have an LCD (3"
screen) color TV that is about 10 years old. When driven from a
composite video input (from a DVD player) it looks fine. But the
broadcast signals are starting to look a bit green.

Not sure if NTSC works the same but the PAL system only recovers R-L & B-L
from the transmitted carrier, green is recovered by working out its
amplitude from the sum of the R & B signals subtracted from the luma signal.
 
Hmmm, just sort of in relation to this thread: can anyone tell me if
its worth repairing my Trinitron? Model: G420S.

The red is pretty much dead now, and the blue sometimes work and
sometimes doesn't. For the most part, the green is fine. Here's a video
of it a few months ago (it would flash during warming up but would
eventually stabilize, but the video shows it's totally crapping it...
turning it OFF then ON would fix this):

http://www.samaseysan.com/temporary/Trinny_neardeathexperience.avi
 
J

James Sweet

Jan 1, 1970
0
Hmmm, just sort of in relation to this thread: can anyone tell me if
its worth repairing my Trinitron? Model: G420S.

The red is pretty much dead now, and the blue sometimes work and
sometimes doesn't. For the most part, the green is fine. Here's a video
of it a few months ago (it would flash during warming up but would
eventually stabilize, but the video shows it's totally crapping it...
turning it OFF then ON would fix this):

http://www.samaseysan.com/temporary/Trinny_neardeathexperience.avi


It's worth trying to resolder the neck board, that may be all it needs.
 
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