This is very strange. My buddy has a 36 inch Panasonic Model CT36SF36
that suddenly
started displaying a rainbow pattern of colors that looks like a
bullseye. In other words there are circular bands of color
superimposed over the screen. The colors are transparent. You can see
a sharp picture that is mostly black and white, but sharp.

I doubt this is a normal degaussing problem. The bands are too
circular. There is a bit of
pulling in of the picture at the corners, as if the power is a bit
low.

Of course, the sets normal controls have no effect on the problem. The
set was not dropped
or otherwise physically damaged. The audio is normal.

This is a big heavy set, swapping out parts is not practical. Has
anyone ever seen this
problem?

I'd still approach it as a degaussing problem. Did somebody hold a strong
magnet up to the screen?

distar97 wrote:
This is very strange. My buddy has a 36 inch Panasonic Model CT36SF36
that suddenly
started displaying a rainbow pattern of colors that looks like a
bullseye. In other words there are circular bands of color
superimposed over the screen. The colors are transparent. You can see
a sharp picture that is mostly black and white, but sharp.

I doubt this is a normal degaussing problem. The bands are too
circular. There is a bit of
pulling in of the picture at the corners, as if the power is a bit
low.

Of course, the sets normal controls have no effect on the problem. The
set was not dropped
or otherwise physically damaged. The audio is normal.

This is a big heavy set, swapping out parts is not practical. Has
anyone ever seen this
problem?

sounds like a little AC 50/60 Hz getting in the supply system somewhere?

Maybe the heater on the Tube has shorted to the system ?
or bad cap in the system?
etc..
Just a guess..

Either that, some one has a magnet or something like it near it.


--
"I'm never wrong, once i thought i was, but was mistaken"
Real Programmers Do things like this.
http://webpages.charter.net/jamie_5

No, it wasn't external magnets, speakers or other outside magnetic
source. (no kids in house or others that may have
accidentally done something)
It could be some internal failure such as tube heater, caps, or stray
AC. I prefer to save those type things for last.

Could there be a flaw in the degauss circuit? It looks too organized
too be the typical magnetic problem. Round circular color bands in
blue,red and green centered on the screen do not appear like other
screens I've seen where kids were involved with magnets or nearby
speakers.

Perhaps I can post a picture of what I'm seeing. I'll try and get a
decent image up this weekend. Check later.

All opinions are useful to me, I'll want to consider everything before
I eventually open this back breaker up.
Thanks, Denis

distar97 writes:

No, it wasn't external magnets, speakers or other outside magnetic
source. (no kids in house or others that may have
accidentally done something)
It could be some internal failure such as tube heater, caps, or stray
AC. I prefer to save those type things for last.

It's not stray magnetic fields or the tube heater (that probably runs
from the flyback).

And I assume it didn't fall on its face - which could distort the shadow
mask to produce a similar result.

But you said the picture looked stretched at the corners?

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.


Could there be a flaw in the degauss circuit? It looks too organized
too be the typical magnetic problem. Round circular color bands in
blue,red and green centered on the screen do not appear like other
screens I've seen where kids were involved with magnets or nearby
speakers.

Perhaps I can post a picture of what I'm seeing. I'll try and get a
decent image up this weekend. Check later.

All opinions are useful to me, I'll want to consider everything before
I eventually open this back breaker up.
Thanks, Denis

Sam G. said:
"And I assume it didn't fall on its face - which could distort the
shadow
mask to produce a similar result.
But you said the picture looked stretched at the corners"?

Sam, thanks for your response... No the set did not fall or suffer any
kind of physical damage that would have
damaged the mask.
I don't have a color bar generator handy, but I noticed that
programming that should have vivid color looks as if the color
adjustment was turned down, sometimes as if it were a B&W show. But if
you ignore the colors, the picture
is still sharp. In fact my buddy joked the set is fine for a color-
blind person.

The picture is not stretched but is pulled in a little at the corners.
Not much though. It varies from channel to channel. It reminds me of
what happens during a power brown-out. It's a minor observation
compared to the circular rainbow problem.
If I can get good representative photos, I'll post them on my personal
site for easy viewing.
Thanks Denis

distar97 wrote:
I doubt this is a normal degaussing problem.

Always degauss anyway.

Years back I went on a service call. The problem was a complete and utter
mystery to me; the colors were random and rainbow-like all over the
screen, but the purity was PERFECT. Gray scale was PERFECT. Red purity
was perfect, as was green purity and blue purity. At this particular
shop the rule was to call the head tech before giving up, so I called
and the tech told me to degauss.

It fixed the problem.

THEN it occurred to me that there was a thunderstorm the previous day,
and this customer was in the area that got hit hard. I asked her if she
had experienced anything out of the ordinary and she told me that they
took a lightning strike directly into the asphalt-paved lot next door.
I still have no idea how the purity could be so perfect while the
shadow mask was magnetized.

--
Postulate a group whose intent is to destroy the United States from within
via anarchy and bankruptcy. The actions of the United States Congress are
completely consistent with the actions one would predict from such a group.

distar97 wrote in news:1184359891.280300.267520
@w3g2000hsg.googlegroups.com:

This is very strange. My buddy has a 36 inch Panasonic Model CT36SF36
that suddenly
started displaying a rainbow pattern of colors that looks like a
bullseye. In other words there are circular bands of color
superimposed over the screen. The colors are transparent. You can see
a sharp picture that is mostly black and white, but sharp.

I doubt this is a normal degaussing problem. The bands are too
circular. There is a bit of
pulling in of the picture at the corners, as if the power is a bit
low.

Of course, the sets normal controls have no effect on the problem. The
set was not dropped
or otherwise physically damaged. The audio is normal.

This is a big heavy set, swapping out parts is not practical. Has
anyone ever seen this
problem?


Check the magnetic field coil correction system, Larger sets greater
than anout 32" usually have a coil on the inside, fed with a modified
pulse with some dc to correct for the earth's magnetic field.

If the circuit has failed there may be too much dc on this coil...

Simply unplug the coil and demagnitise the CRT. If that corrects the
problem you know for shure where to look. This is not the degaussing
coil it is smaller and closer to the yoke (deflection coils).

R!!

The screen may be magnetized. The internal degausser may not be
working.

If the fault is not the internal degalusser, it is possible that the
shadow mask in the tube has become defective.

Both of these types of faults are comon.


Jerry G.
======







On Jul 13, 4:51 pm, distar97 wrote:
This is very strange. My buddy has a 36 inch Panasonic Model CT36SF36
that suddenly
started displaying a rainbow pattern of colors that looks like a
bullseye. In other words there are circular bands of color
superimposed over the screen. The colors are transparent. You can see
a sharp picture that is mostly black and white, but sharp.

I doubt this is a normal degaussing problem. The bands are too
circular. There is a bit of
pulling in of the picture at the corners, as if the power is a bit
low.

Of course, the sets normal controls have no effect on the problem. The
set was not dropped
or otherwise physically damaged. The audio is normal.

This is a big heavy set, swapping out parts is not practical. Has
anyone ever seen this
problem?

distar97 writes:

Sam G. said:
"And I assume it didn't fall on its face - which could distort the
shadow
mask to produce a similar result.
But you said the picture looked stretched at the corners"?

Sam, thanks for your response... No the set did not fall or suffer any
kind of physical damage that would have
damaged the mask.
I don't have a color bar generator handy, but I noticed that
programming that should have vivid color looks as if the color
adjustment was turned down, sometimes as if it were a B&W show. But if
you ignore the colors, the picture
is still sharp. In fact my buddy joked the set is fine for a color-
blind person.

The picture is not stretched but is pulled in a little at the corners.
Not much though. It varies from channel to channel. It reminds me of
what happens during a power brown-out. It's a minor observation
compared to the circular rainbow problem.
If I can get good representative photos, I'll post them on my personal
site for easy viewing.

Could that have been preexisting condition that you just noticed?

In any case, as others have suggested, try degaussing the set before
digging deeper.

--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.

Change the degauss thermistor, resolder the connections where the degauss
harness plugs into the main chassis, check if there is a degauss relay in
the circuit, if so change it also.
Seen a lot of large screen Panasonics, Samsungs, Sonys, RCA, Etc with very
similar problems due to failures in the degauss circuitry. Also seen many
dead sets with open fuse devises because the degauss thermistor actually
changes its resistance value, which eventually blows the main fuse because
of he additional current demand.
"Jerry G." wrote in message
ups.com...

The screen may be magnetized. The internal degausser may not be
working.

If the fault is not the internal degalusser, it is possible that the
shadow mask in the tube has become defective.

Both of these types of faults are comon.


Jerry G.
======







On Jul 13, 4:51 pm, distar97 wrote:
This is very strange. My buddy has a 36 inch Panasonic Model CT36SF36
that suddenly
started displaying a rainbow pattern of colors that looks like a
bullseye. In other words there are circular bands of color
superimposed over the screen. The colors are transparent. You can see
a sharp picture that is mostly black and white, but sharp.

I doubt this is a normal degaussing problem. The bands are too
circular. There is a bit of
pulling in of the picture at the corners, as if the power is a bit
low.

Of course, the sets normal controls have no effect on the problem. The
set was not dropped
or otherwise physically damaged. The audio is normal.

This is a big heavy set, swapping out parts is not practical. Has
anyone ever seen this
problem?

On Jul 14, 9:49 am, "AJ" wrote:
Change the degauss thermistor, resolder the connections where the degauss
harness plugs into the main chassis, check if there is a degauss relay in
the circuit, if so change it also.
Seen a lot of large screen Panasonics, Samsungs, Sonys, RCA, Etc with very
similar problems due to failures in the degauss circuitry. Also seen many
dead sets with open fuse devises because the degauss thermistor actually
changes its resistance value, which eventually blows the main fuse because
of he additional current demand."Jerry G." wrote in message

ups.com...





The screen may be magnetized. The internal degausser may not be
working.

If the fault is not the internal degalusser, it is possible that the
shadow mask in the tube has become defective.

Both of these types of faults are comon.

Jerry G.
======

On Jul 13, 4:51 pm, distar97 wrote:
This is very strange. My buddy has a 36 inch Panasonic Model CT36SF36
that suddenly
started displaying a rainbow pattern of colors that looks like a
bullseye. In other words there are circular bands of color
superimposed over the screen. The colors are transparent. You can see
a sharp picture that is mostly black and white, but sharp.

I doubt this is a normal degaussing problem. The bands are too
circular. There is a bit of
pulling in of the picture at the corners, as if the power is a bit
low.

Of course, the sets normal controls have no effect on the problem. The
set was not dropped
or otherwise physically damaged. The audio is normal.

This is a big heavy set, swapping out parts is not practical. Has
anyone ever seen this
problem?- Hide quoted text -

- Show quoted text -

Just take a strong magnet and wave it around the face of the tube
moving back gradually. See what that does.

H. R. (Bob) Hofmann

Thanks to all for the advise. Good response. I'll check it out. In the
meantime I took some pictures.
You can see them on a page I set up off-board Go to:
distar97 daht googlepages daht kom sellash tvrainbow (I hate robots,
sorry) Note: do not include www

Thanks to all

On 14 jul, 16:49, "AJ" wrote:
Change the degauss thermistor, resolder the connections where the degauss
harness plugs into the main chassis, check if there is a degauss relay in
the circuit, if so change it also.
Seen a lot of large screen Panasonics, Samsungs, Sonys, RCA, Etc with very
similar problems due to failures in the degauss circuitry.

that is excellent advice from AJ, Don't rule out the possibility of a
degauss problem. You will need to open 'er up and check the degauss
cct so as to be able to eliminate this as the most likelly cause.

-b.