TV - Purple Patch

Hi all

Probably not strictly a digital TV issue but still..........

Over the last week our 9 year old Panasonic Quintrix TV has developed a
purple "splodge" in the centre of the screen.
I say purple because this is the most commonly seen colour in the
distortion.
Funny when the image is a full face news caster as they appear to have a
black eye on occasions.

Can anyone explain the cause please?
Presumably this is a failure of one or more electron guns.

TIA

Phil

In article ,
TheScullster wrote:
Hi all

Probably not strictly a digital TV issue but still..........

Over the last week our 9 year old Panasonic Quintrix TV has developed a
purple "splodge" in the centre of the screen.
I say purple because this is the most commonly seen colour in the
distortion.
Funny when the image is a full face news caster as they appear to have a
black eye on occasions.

Can anyone explain the cause please?
Presumably this is a failure of one or more electron guns.

I suspect the set needs degaussing. Do turn it on and off at the mains,
ever? A mains switch on usually operates the internal degaussing circuitry.

Have you been putting anything magnetic near the screen, such as a
loudspeaker? That could be the original cause.

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

On Mon, 03 Sep 2007 08:52:31 +0100, charles
mused:

In article ,
TheScullster wrote:
Hi all

Probably not strictly a digital TV issue but still..........

Over the last week our 9 year old Panasonic Quintrix TV has developed a
purple "splodge" in the centre of the screen.
I say purple because this is the most commonly seen colour in the
distortion.
Funny when the image is a full face news caster as they appear to have a
black eye on occasions.

Can anyone explain the cause please?
Presumably this is a failure of one or more electron guns.

I suspect the set needs degaussing. Do turn it on and off at the mains,
ever? A mains switch on usually operates the internal degaussing circuitry.

Assuming the purple circle isn't caused by faulty mags or thermistors
in the degaussing circuit.

Have you been putting anything magnetic near the screen, such as a
loudspeaker? That could be the original cause.
--
Regards,
Stuart.

"TheScullster" wrote in message
. uk...
Hi all

Probably not strictly a digital TV issue but still..........

Over the last week our 9 year old Panasonic Quintrix TV has developed a
purple "splodge" in the centre of the screen.
I say purple because this is the most commonly seen colour in the
distortion.
Funny when the image is a full face news caster as they appear to have a
black eye on occasions.

Can anyone explain the cause please?
Presumably this is a failure of one or more electron guns.

The degaussing thermistor could have become dry jointed, or even have
disintegrated internally. In rare cases the shadow mask may have distorted,
or if it only occurs when the set gets warm it could be Doming

http://en.wikipedia.org/wiki/Doming_%28television%29 in which case try
reducing the brightness and contrast settings.


TIA

Phil

In article ,
TheScullster wrote:
Hi all

Probably not strictly a digital TV issue but still..........

Over the last week our 9 year old Panasonic Quintrix TV has developed a
purple "splodge" in the centre of the screen.
I say purple because this is the most commonly seen colour in the
distortion.
Funny when the image is a full face news caster as they appear to have a
black eye on occasions.

Can anyone explain the cause please?
Presumably this is a failure of one or more electron guns.

Sounds like it's been got at by a powerful magnet. Has a speaker etc been
placed close to the set or moved past it but close by? Other possibility
is a computer disc drive.

Try turning it off on the set's switch - not remote or mains socket. And
power up again which should operate the de-gaussing circuit. It might take
several goes. If this doesn't cure it the next thing to try is an external
degaussing device - a decent repair man should have one.

--
*Ham and Eggs: Just a day's work for a chicken, but a lifetime commitment

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote


Sounds like it's been got at by a powerful magnet. Has a speaker etc been
placed close to the set or moved past it but close by? Other possibility
is a computer disc drive.

Try turning it off on the set's switch - not remote or mains socket. And
power up again which should operate the de-gaussing circuit. It might take
several goes. If this doesn't cure it the next thing to try is an external
degaussing device - a decent repair man should have one.

--

Thanks to all respondents.
This problem does seem to coincide with the arrival of some magnet-stoney
type things in the childrens' toy armoury!
Where would the magnets have to be placed to cause this problem?
The TV is switched off at a front on-off switch when not in use, but rarely
powered off at the wall - the degauss operation should occur with a positive
switch-off at the TV shouldn't it?

Thanks again

Phil

TheScullster wrote:
....
Where would the magnets have to be placed to cause this problem?
The TV is switched off at a front on-off switch when not in use, but rarely
powered off at the wall - the degauss operation should occur with a positive
switch-off at the TV shouldn't it?
The kids probably noticed their magnets had a funny distorting effect on
the screen :-)

Switch on should trigger a degauss if set has been off for a bit, but as
has already been said, the circuit may be duff.

In article , TheScullster wrote:
Thanks to all respondents.
This problem does seem to coincide with the arrival of some magnet-stoney*
type things in the childrens' toy armoury!
Where would the magnets have to be placed to cause this problem?
The TV is switched off at a front on-off switch when not in use, but rarely*
powered off at the wall - the degauss operation should occur with a positive*
switch-off at the TV shouldn't it?

Yes, but leave it switched off for a while. The built-in degaussing circuit
works by producing a large AC field that decays in a few seconds by means of a
thermistor - a component that changes its resistance as it warms up. You need
to allow time for it to cool down before it will work again. Try at least 10
minutes.

This scheme was invented in the days before remote controls, when the only
mains switch would have been a traditional mechanical one, so everything was
properly disconnected with an airgap when the TV was switched off, and every
time it was switched on it would be switched on from cold.

Rod.

On Mon, 03 Sep 2007 11:35:13 +0100, OldBill
wrote:

TheScullster wrote:
...
Where would the magnets have to be placed to cause this problem?
The TV is switched off at a front on-off switch when not in use, but rarely
powered off at the wall - the degauss operation should occur with a positive
switch-off at the TV shouldn't it?
The kids probably noticed their magnets had a funny distorting effect on
the screen :-)

Switch on should trigger a degauss if set has been off for a bit, but as
has already been said, the circuit may be duff.

My son had hours of fun with his new magnet and our TV set - until I
arrived home!
--
Cheers

Peter

In article , TheScullster
scribeth thus

"Dave Plowman (News)" wrote


Sounds like it's been got at by a powerful magnet. Has a speaker etc been
placed close to the set or moved past it but close by? Other possibility
is a computer disc drive.

Try turning it off on the set's switch - not remote or mains socket. And
power up again which should operate the de-gaussing circuit. It might take
several goes. If this doesn't cure it the next thing to try is an external
degaussing device - a decent repair man should have one.

--

Thanks to all respondents.
This problem does seem to coincide with the arrival of some magnet-stoney
type things in the childrens' toy armoury!
Where would the magnets have to be placed to cause this problem?
The TV is switched off at a front on-off switch when not in use, but rarely
powered off at the wall - the degauss operation should occur with a positive
switch-off at the TV shouldn't it?

Thanks again

Phil



Not recommend this .. but it does work!..

Get one of the toys and tie it to a bit of string and twist it well till
its spinning then move it close to the screen while the TV is one and
you will see lots of odd moving colours, take it away slowly whilst
spinning and the colours will weaken and eventually disappear as will
the coloured patch.

That is in effect what a degaussing coil does!...
--
Tony Sayer