Dull red from a video projector

[N_Cook]

As though the red of the colour wheel has gone dark with age. Instead of
vibrant red it is dull red/brown. Improved a bit with up to the limits
changes to the colour matrix, now dull red rather than dark brown for a
saturated red input . Not a leads problem , computer in and then computer
out to a monitor is fine. Video source is similarly affected. No loose leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across different
makes and models?

 

[William Sommerwerck]

I have no idea if it's commonplace, but the cause is likely related to the
effect of photographs and advertisements turning magenta under exposure to
daylight.

The red filter is red because it absorbs green and blue light. Blue light is
most-effective at breaking molecular bonds, as its photons have the highest
energy. QED?

It might also be that the designers chose a poor-quality dye for the filter.

 

[N_Cook]

William Sommerwerck <grizzledgeezer@comcast.net> wrote in message
news:k5m4if$qqe$1@dont-email.me...

I have no idea if it's commonplace, but the cause is likely related to the
effect of photographs and advertisements turning magenta under exposure to
daylight.

The red filter is red because it absorbs green and blue light. Blue light
is
most-effective at breaking molecular bonds, as its photons have the
highest
energy. QED?

It might also be that the designers chose a poor-quality dye for the
filter.

Perhaps the dystuff centrifuges out to the edge ;-(
I'm surprised these colour wheels hold together as they seem to be
individual glass sectors super-glued into a disc.

 

[Adrian Tuddenham]

N_Cook <diverse@tcp.co.uk> wrote:

As though the red of the colour wheel has gone dark with age. Instead of
vibrant red it is dull red/brown. Improved a bit with up to the limits
changes to the colour matrix, now dull red rather than dark brown for a
saturated red input . Not a leads problem , computer in and then computer
out to a monitor is fine. Video source is similarly affected. No loose leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across different
makes and models?

Is there any easy way to look at the colour wheel and see if the filter
really is the problem.

Could it be the lamp failing in some strange way? You can get a rough
idea of the spectrum if there is some light spillage which has not come
through the colour wheel (reflections coming out of ventilation slots in
the projector, for instance). Take one of the clear CDs that is used to
protect the bottom of a pack and, taking care not to get any
fingerprints on the disc, hold it so that the tip of your nose is poking
through the centre hole. Close one eye and move your head so that the
light from the lamp appears above the top edge of the disc.

If the light source appears sufficiently small, you should see a clear
spectrum with a good quantity of each colour.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

 

[N_Cook]

Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote in message
news:1ks46k0.uhuuqy1wgemkgN%adrian@poppyrecords.invalid.invalid...

N_Cook <diverse@tcp.co.uk> wrote:

As though the red of the colour wheel has gone dark with age. Instead of
vibrant red it is dull red/brown. Improved a bit with up to the limits
changes to the colour matrix, now dull red rather than dark brown for a
saturated red input . Not a leads problem , computer in and then
computer
out to a monitor is fine. Video source is similarly affected. No loose
leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across
different
makes and models?

Is there any easy way to look at the colour wheel and see if the filter
really is the problem.

Could it be the lamp failing in some strange way? You can get a rough
idea of the spectrum if there is some light spillage which has not come
through the colour wheel (reflections coming out of ventilation slots in
the projector, for instance). Take one of the clear CDs that is used to
protect the bottom of a pack and, taking care not to get any
fingerprints on the disc, hold it so that the tip of your nose is poking
through the centre hole. Close one eye and move your head so that the
light from the lamp appears above the top edge of the disc.

If the light source appears sufficiently small, you should see a clear
spectrum with a good quantity of each colour.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

What an intriguing test, I'll make sure no one can see me while doing it,
they may phone up the funny-farm.
(look, the loon has taken to playing CDs with his nose)
The lamp spillage looks normal white but
if such a spectrum test shows an absence of red it would be useful
elimination test. Would your "CD" difraction grating disc yest work with any
lamp souurce for comparison say car headlight or a xenon floodlight bulb
just to see what a complete spectrum would look like with such a disc.

 

[Adrian Tuddenham]

N_Cook <diverse@tcp.co.uk> wrote:

Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote in message
news:1ks46k0.uhuuqy1wgemkgN%adrian@poppyrecords.invalid.invalid...
N_Cook <diverse@tcp.co.uk> wrote:

As though the red of the colour wheel has gone dark with age. Instead of
vibrant red it is dull red/brown. Improved a bit with up to the limits
changes to the colour matrix, now dull red rather than dark brown for a
saturated red input . Not a leads problem , computer in and then
computer
out to a monitor is fine. Video source is similarly affected. No loose
leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across
different
makes and models?

Is there any easy way to look at the colour wheel and see if the filter
really is the problem.

Could it be the lamp failing in some strange way? You can get a rough
idea of the spectrum if there is some light spillage which has not come
through the colour wheel (reflections coming out of ventilation slots in
the projector, for instance). Take one of the clear CDs that is used to
protect the bottom of a pack and, taking care not to get any
fingerprints on the disc, hold it so that the tip of your nose is poking
through the centre hole. Close one eye and move your head so that the
light from the lamp appears above the top edge of the disc.

If the light source appears sufficiently small, you should see a clear
spectrum with a good quantity of each colour.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk


What an intriguing test, I'll make sure no one can see me while doing it,
they may phone up the funny-farm.
(look, the loon has taken to playing CDs with his nose)

I once demonstrated it at a coffe morning of the Bath Royal Literary &
Scientific Institution. After handing out half a dozen discs, I had a
great time watching them trying it out (pity I didn't take a
photograph).

The lamp spillage looks normal white but
if such a spectrum test shows an absence of red it would be useful
elimination test.

I would have thought that a normal-looking white would suggest that the
lamp is OK - although I suppose there is a faint possibility that some
sort of filtering or correction system could be upset by the absence of
some parts of the spectrum which are too narrow to affect the overall
appearance.

Would your "CD" difraction grating disc yest work with any
lamp souurce for comparison say car headlight or a xenon floodlight bulb
just to see what a complete spectrum would look like with such a disc.

It works with any source, but the image you view should be as small as
possible if you want to see any detail of lines or holes in the
spectrum. You can either mask-down a large source or stand a distance
away from it.

I've just tried the test with my own projector and the lamphouse spill
shows a fairly continuous band with a couple of strong lines in the
green and one in the cyan. I have tried to photograph it for you, but
the bands don't show up:

http://www.poppyrecords.co.uk/other/images/CBAT01_1122.JPG

With the screen set to 'black', the residual light coming through the
lens appears a bit stronger in the red region and the lines are not
noticeable, so I suspect there is some correction going on.

The light seen through one of the other vents appears to be a very
strange magenta-ish colour (too diffuse to analyse with the CD). I
would guess that this is coming out of the back of the lamp and is the
unwanted transmission from a dichroic mirror.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

 

[Klaatu]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:k5log6$q26$1@dont-email.me...

As though the red of the colour wheel has gone dark with age. Instead of
vibrant red it is dull red/brown. Improved a bit with up to the limits
changes to the colour matrix, now dull red rather than dark brown for a
saturated red input . Not a leads problem , computer in and then computer
out to a monitor is fine. Video source is similarly affected. No loose
leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across different
makes and models?

Had that intermittent problem with an Epson (?) DLP projector. Blue and
green were fine, red was brown sometimes, cable seemed fine, but replaced it
anyway. Problem disappeared.

 

[Jon Elson]

Klaatu wrote:

Had that intermittent problem with an Epson (?) DLP projector. Blue and
green were fine, red was brown sometimes, cable seemed fine, but replaced
it
anyway. Problem disappeared.
Yes, an excellent point! Can this projector display any setup or splash

page? Does that also have the bad red? If the splash page is good, then
it very well could be the cable. I have several LCD monitors that
sometimes shift colors when the cable is bumped, must be poor contacts
on the connectors. This would be especially true with analog video signals.

Jon

 

[N_Cook]

Jon Elson <jmelson@wustl.edu> wrote in message
news:Sb-dnVps6r-nveLNnZ2dnUVZ_sqdnZ2d@giganews.com...

Klaatu wrote:



Had that intermittent problem with an Epson (?) DLP projector. Blue and
green were fine, red was brown sometimes, cable seemed fine, but
replaced
it
anyway. Problem disappeared.
Yes, an excellent point! Can this projector display any setup or splash
page? Does that also have the bad red? If the splash page is good, then
it very well could be the cable. I have several LCD monitors that
sometimes shift colors when the cable is bumped, must be poor contacts
on the connectors. This would be especially true with analog video
signals.

Jon

The menu structure is that functions selected are designated vy changing
blue to red lettering so are not that obvious as highlighted

 

[N_Cook]

Klaatu <whichway@today.org> wrote in message
news:IsKdncz_zMU_cePNnZ2dnUVZ_oudnZ2d@giganews.com...

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:k5log6$q26$1@dont-email.me...
As though the red of the colour wheel has gone dark with age. Instead of
vibrant red it is dull red/brown. Improved a bit with up to the limits
changes to the colour matrix, now dull red rather than dark brown for a
saturated red input . Not a leads problem , computer in and then
computer
out to a monitor is fine. Video source is similarly affected. No loose
leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across
different
makes and models?



Had that intermittent problem with an Epson (?) DLP projector. Blue and
green were fine, red was brown sometimes, cable seemed fine, but replaced
it
anyway. Problem disappeared.

So you replaced the cable?
As the monitor out seems fine I assumed it could not be a cable problem

 

[N_Cook]

Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote in message
news:1ks4dq9.1265xe219qw1hcN%adrian@poppyrecords.invalid.invalid...

N_Cook <diverse@tcp.co.uk> wrote:

Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote in message
news:1ks46k0.uhuuqy1wgemkgN%adrian@poppyrecords.invalid.invalid...
N_Cook <diverse@tcp.co.uk> wrote:

As though the red of the colour wheel has gone dark with age.
Instead of
vibrant red it is dull red/brown. Improved a bit with up to the
limits
changes to the colour matrix, now dull red rather than dark brown
for a
saturated red input . Not a leads problem , computer in and then
computer
out to a monitor is fine. Video source is similarly affected. No
loose
leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across
different
makes and models?

Is there any easy way to look at the colour wheel and see if the
filter
really is the problem.

Could it be the lamp failing in some strange way? You can get a rough
idea of the spectrum if there is some light spillage which has not
come
through the colour wheel (reflections coming out of ventilation slots
in
the projector, for instance). Take one of the clear CDs that is used
to
protect the bottom of a pack and, taking care not to get any
fingerprints on the disc, hold it so that the tip of your nose is
poking
through the centre hole. Close one eye and move your head so that the
light from the lamp appears above the top edge of the disc.

If the light source appears sufficiently small, you should see a clear
spectrum with a good quantity of each colour.

--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk


What an intriguing test, I'll make sure no one can see me while doing
it,
they may phone up the funny-farm.
(look, the loon has taken to playing CDs with his nose)

I once demonstrated it at a coffe morning of the Bath Royal Literary &
Scientific Institution. After handing out half a dozen discs, I had a
great time watching them trying it out (pity I didn't take a
photograph).

The lamp spillage looks normal white but
if such a spectrum test shows an absence of red it would be useful
elimination test.

I would have thought that a normal-looking white would suggest that the
lamp is OK - although I suppose there is a faint possibility that some
sort of filtering or correction system could be upset by the absence of
some parts of the spectrum which are too narrow to affect the overall
appearance.

Would your "CD" difraction grating disc yest work with any
lamp souurce for comparison say car headlight or a xenon floodlight bulb
just to see what a complete spectrum would look like with such a disc.

It works with any source, but the image you view should be as small as
possible if you want to see any detail of lines or holes in the
spectrum. You can either mask-down a large source or stand a distance
away from it.

I've just tried the test with my own projector and the lamphouse spill
shows a fairly continuous band with a couple of strong lines in the
green and one in the cyan. I have tried to photograph it for you, but
the bands don't show up:

http://www.poppyrecords.co.uk/other/images/CBAT01_1122.JPG

With the screen set to 'black', the residual light coming through the
lens appears a bit stronger in the red region and the lines are not
noticeable, so I suspect there is some correction going on.

The light seen through one of the other vents appears to be a very
strange magenta-ish colour (too diffuse to analyse with the CD). I
would guess that this is coming out of the back of the lamp and is the
unwanted transmission from a dichroic mirror.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

I suppose those discs are rejects from the pitting stage so never go on to
the matalising stage.

I tried with some LEDs , the most convincing was "point source" non diffused
blue, just a slight bit of green in the spectrum with the blue. Even orange
lens over a neon was quite convincing. The more light the less convincing
presumably because the eye is overloaded with the most prominent allowing
the minor spectra components to be more prominent

Through one section of the fan louvres you can see part of the dichroic
mirror and that is distinctly red when the lamp is on , I wonder if the
dichroic plating? can break down over time and stop reflecting red and
absorbing it instead, ie passing red and infra-red light.

If I get inside again I may try mounting a piece of mirror in the lamp light
path and try reflecting a red LED laser into the light tunnel and
colourwheel and see if that brings up the red component/s of the image

 

[Adrian Tuddenham]

N_Cook <diverse@tcp.co.uk> wrote:

[...]

If I get inside again I may try mounting a piece of mirror in the lamp light
path and try reflecting a red LED laser into the light tunnel and
colourwheel and see if that brings up the red component/s of the image

Don't risk damaging your eyes, a focussed arc lamp is a dangerous
beast*. If you can see inside with the machine switched off, it would
make more sense to just look at the red sector of the colour wheel and
see if it has turned brown.

I am begining to think that the other respondents have got better
suggestions and the problem is more likely to lie in the cables, the
signal, or even the colour-handling software.



* These lamps are dangerous in other ways, too. I once had to replace
one which had burst after a cooling failure, the explosion had bent a
0.375"-thick extruded alloy heatsink.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

 

[N_Cook]

Adrian Tuddenham <adrian@poppyrecords.invalid.invalid> wrote in message
news:1ks5ojr.1vz1mndfyw1y2N%adrian@poppyrecords.invalid.invalid...

N_Cook <diverse@tcp.co.uk> wrote:

[...]

If I get inside again I may try mounting a piece of mirror in the lamp
light
path and try reflecting a red LED laser into the light tunnel and
colourwheel and see if that brings up the red component/s of the image

Don't risk damaging your eyes, a focussed arc lamp is a dangerous
beast*. If you can see inside with the machine switched off, it would
make more sense to just look at the red sector of the colour wheel and
see if it has turned brown.

I am begining to think that the other respondents have got better
suggestions and the problem is more likely to lie in the cables, the
signal, or even the colour-handling software.



* These lamps are dangerous in other ways, too. I once had to replace
one which had burst after a cooling failure, the explosion had bent a
0.375"-thick extruded alloy heatsink.


--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk

Not just the bright light , but the cooling is disrupted by removing the
cover. I drape silicone sheet over wonen glass mat over the active area to
obviate shatter, intense light/UV, venting pitfalls.

 

[N_Cook]

The spill over light gives plenty of red on the "difraction grating". I see
this "blank CD/DVD" has a big clear patch on its surface, so those discs are
rejects from the first stage of production

 

[Klaatu]

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:k5obpg$hpp$2@dont-email.me...

Klaatu <whichway@today.org> wrote in message
news:IsKdncz_zMU_cePNnZ2dnUVZ_oudnZ2d@giganews.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:k5log6$q26$1@dont-email.me...
As though the red of the colour wheel has gone dark with age. Instead
of
vibrant red it is dull red/brown. Improved a bit with up to the limits
changes to the colour matrix, now dull red rather than dark brown for a
saturated red input . Not a leads problem , computer in and then
computer
out to a monitor is fine. Video source is similarly affected. No loose
leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across
different
makes and models?



Had that intermittent problem with an Epson (?) DLP projector. Blue and
green were fine, red was brown sometimes, cable seemed fine, but replaced
it
anyway. Problem disappeared.


So you replaced the cable?
As the monitor out seems fine I assumed it could not be a cable problem

Yes, replaced the cable, problem disappeared. Since it was used with a
laptop, I suspect a bad pin or socket. When the problem stopped with a new
cable, I stopped looking.
BTW, the problem hasn't reappeared.

 

[N_Cook]

Klaatu <whichway@today.org> wrote in message
news:T4Kdnfh4IYXZsx7NnZ2dnUVZ_qOdnZ2d@giganews.com...

"N_Cook" <diverse@tcp.co.uk> wrote in message
news:k5obpg$hpp$2@dont-email.me...
Klaatu <whichway@today.org> wrote in message
news:IsKdncz_zMU_cePNnZ2dnUVZ_oudnZ2d@giganews.com...
"N_Cook" <diverse@tcp.co.uk> wrote in message
news:k5log6$q26$1@dont-email.me...
As though the red of the colour wheel has gone dark with age. Instead
of
vibrant red it is dull red/brown. Improved a bit with up to the
limits
changes to the colour matrix, now dull red rather than dark brown for
a
saturated red input . Not a leads problem , computer in and then
computer
out to a monitor is fine. Video source is similarly affected. No
loose
leads
inside. "Service" manual has no schematic of course.
Is there a generic cause to this as it seems quite common across
different
makes and models?



Had that intermittent problem with an Epson (?) DLP projector. Blue
and
green were fine, red was brown sometimes, cable seemed fine, but
replaced
it
anyway. Problem disappeared.


So you replaced the cable?
As the monitor out seems fine I assumed it could not be a cable problem



Yes, replaced the cable, problem disappeared. Since it was used with a
laptop, I suspect a bad pin or socket. When the problem stopped with a
new
cable, I stopped looking.
BTW, the problem hasn't reappeared.

Tried another cable but the same absence of red

 

This thread is a bit confusing. To got one person talking about a color wheel and another talking about a dichroic mirror.

The twain shall never meet. there can be a DLP without a color wheel, but it will be a three panel and it will have dichroic mirrors. Though I don't believe it has been done, there could be an LCD with a color wheel, but it would need one superfast refresh panel.

Why don't you just post the model number.

You have two completely different scenarios here, and one main point, is the red dull in the OSD generated inside ?

If it is a three panel of whatever type, and the fault appears in the menus, you are looking at a fried dichroic. If it is a one panel it is most likely the color wheel but a physical inspection is warranted.

If it only has a three section color wheel that's one thing. They just are n ot very likely to fail in that way. If they do you will see it, there should be a band where the light was. If it has a seven segment color wheel, yes it could quite have darkened but it's not all that likely.

Incidentally one brand of these does get a fault in which the red section of the seven segment wheel breaks free and then not only is the color screwed up, the thing vibrates like all hell.

Why no model number ? Or did I miss it ? I do believe I read the thread here. Hell, I might have the service manual on my harddrive. sure you have it, but I don't know what this thing is and we don't even know if it's a DLP or LCD or lycos or what.

If it's a seven segment color wheel and the red looks good, it probably is in the signal processing. That is a whole different basllpark.

J

 

[N_Cook]

<jurb6006@gmail.com> wrote in message
news:b1d4d344-5fbe-4151-866e-16d22d22015b@googlegroups.com...
This thread is a bit confusing. To got one person talking about a color
wheel and another talking about a dichroic mirror.

The twain shall never meet. there can be a DLP without a color wheel, but it
will be a three panel and it will have dichroic mirrors. Though I don't
believe it has been done, there could be an LCD with a color wheel, but it
would need one superfast refresh panel.

Why don't you just post the model number.

You have two completely different scenarios here, and one main point, is the
red dull in the OSD generated inside ?

If it is a three panel of whatever type, and the fault appears in the menus,
you are looking at a fried dichroic. If it is a one panel it is most likely
the color wheel but a physical inspection is warranted.

If it only has a three section color wheel that's one thing. They just are n
ot very likely to fail in that way. If they do you will see it, there should
be a band where the light was. If it has a seven segment color wheel, yes it
could quite have darkened but it's not all that likely.

Incidentally one brand of these does get a fault in which the red section of
the seven segment wheel breaks free and then not only is the color screwed
up, the thing vibrates like all hell.

Why no model number ? Or did I miss it ? I do believe I read the thread
here. Hell, I might have the service manual on my harddrive. sure you have
it, but I don't know what this thing is and we don't even know if it's a DLP
or LCD or lycos or what.

If it's a seven segment color wheel and the red looks good, it probably is
in the signal processing. That is a whole different basllpark.

J

+++++++

The dichroic is the parabolic reflector behind the discharge lamp, letting
through IR and reflecting visible light. 3 sector colour wheel. If I can rob
a colour wheel from a defunct projector I will try its red sector in the
light path of this one just to check the white areas go red etc in the
output image.
As putting a normal mainly white image through the projector from a graphics
package, ramping up the red slider to 200 so the pc monitor image is redded
out , the projector image is no change in the white areas , so I suspect
signal processing area fault

 

[N_Cook]

This is a Mitsubishi XD200U projector. I've just taken the optical block
apart from an InFocus LP420, RGB when viewing through the colour wheel but
interestingly complements of cyan,yellow , magenta mirroring reflected when
viewed at an angle