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-   -   Is this normal? Distortion in picture (http://www.dvinfo.net/forum/view-video-display-hardware-software/142420-normal-distortion-picture.html)

Philip Pierloz January 26th, 2009 10:12 AM

Is this normal? Distortion in picture
 
I've bought an used TV monitor but I keep getting these distortions of color shifting, mostly in the corners. Some places that need to be red are green, green are blue etc. These spots comes and go. One day is better than the other.

Is this due to the monitor or to my setup? I have a 30d warranty, so I could send hem back, but I need to know if the monitor is the problem. I have placed my monitor everywhere on my desk and I thought I finally had found the right place but now, a couple of days later, it starts again.

I've attached a picture of one of the previous days. For the moment, it's more in the lower right corner the distrotion comes.

http://picasaweb.google.be/lh/photo/...eat=directlink
http://picasaweb.google.be/lh/photo/...eat=directlink

Would this occur again if I would return this one and buy a new monitor (e.g. JVC TM-H150CG)

Chris Soucy January 26th, 2009 01:59 PM

Hi Philip.......................
 
Well, to answer your first question, no, it's not normal.

Is it due to your monitor or your set up?

Ah, now, that's an interesting question.

Off the top of my head, there's two main causes for what I can see.

The first is that the colour mask inside the tube has been displaced or warped due to a shock (dropped etc).

This is terminal and cannot be repaired without replacing the tube.

The second is that the tube is/ has been affected by an external magnetic field which is pulling one of the gun paths out of alignement.

That the phenomina seems to be variable in it's intensity and location leads me to think it's the latter, tho' only tests could confirm it.

Possible culprits?

Unshielded speakers, anything with a power transformer inside, switch mode power supply (outside chance), electric motor(s) or some of that humungous steel framework holding your workbench up getting somehow magnetized (yes, it's visible in the photo).

The problem is that even removing the culprit (or the display from it) may not de - magnetise the display using the inbuilt degauss circuits, which fire up every time the display is turned on.

Given that it would appear to be a "pro" display, it probably has a seperate "degauss" button somewhere.

Removing the display to somewhere where there is no possiblity of outside magnetic interference and repeatedly pressing the "degauss" button MAY clear it, but check the manual for maximum use rates before going mad.

If the inbuilt degauss cannot clear it, it may need professional degaussing, using a device that looks very similar to a thick magicians wand plugged into the mains.

It's an art form and should only be done by someone who's been trained.

Now, what should you do?

Remove the display to somewhere where it cannot be affected by magnetic anything.

Do the "degauss thing".

If it doesn't clear, it's up to you:

1. Send it back

2. Find a repair facility and have them look at it and give you a quote for a fix.

2b. Get it fixed.

2c. Send it back

I'll stay tuned for further developements.


CS

PS: Just re - read you're posts last line. Not knowing the unit you indicated, all I can say is, if it's a CRT monitor, you must eliminate the source of this magnetism (if it is coming from your setup) whatever you do.

If it is your setup at fault, then no CRT's safe.

Don't think you have much of a choice, either prove the current unit faulty, find the source if it's magnetic corruption OR go LCD.

Sverrir Fridriksson January 26th, 2009 02:18 PM

I've only seen stuff like this where an unshielded speaker was nearby. Do what Chris suggests.

Philip Pierloz January 27th, 2009 12:30 PM

My setup is like this:
On the left corner of my table the monitor (a Sony PVM 14L4) and the other corner, some 5 feet away, a LCD display and 2 small computer speakers

The first speaker, a small computer speaker, is about 5 feet away. A much larger (hifi speaker) is some 7 feet away from the tube. The only electronics nearby is a laptop (about 1 foot) and a portable phone. As I've already had a nice picture some days ago, with this same laptop next to it, I'd find it weird that it would be due to the phone and/or laptop.

I think I haven't mentioned it, but manual degaussing won't work. In some cases it even makes it worse.


I just walked around my house and these are my findings:

The distortion comes up everywhere: in rooms without speakers as well as in rooms with speakers, far/close (within 3 feet) to speakers, on the floor, on the table,... but there is always one direction where the picture comes clean. For how long? I can't say that by now. Problem is: I can't change the direction of my editing suite: the desk is fixed.

My desk is made of profiles of steel and wooden planks. We also have spotlights in the house, feeded by transformers (230V -> 12V) in ceiling/floor (ceiling in the rooms mentioned above, floor for my editing desk) Can one of these be the problem?

What's also weird, that so many people are using those monitors and just very little information can be found about this particular problem. Does everybody has the perfect setup at home? I see many people who have monitor speakers within 5 feet of there editing suite and monitor...

Is this a particular problem of professional monitors? Are they a lot more sensitive than consumer CRT's? I've never had any problems with the picture of my old consumer TV.

If it is due to my setup, can this be fixed? And how? Can I ground it and where should I ground it then? Can I e.g. make a case where I can place the monitor in? Other solutions?

Chris Soucy January 27th, 2009 05:30 PM

"My desk is made of profiles of steel and wooden planks. We also have spotlights in the house, feeded by transformers (230V -> 12V) in ceiling/floor (ceiling in the rooms mentioned above, floor for my editing desk) Can one of these be the problem?"

Possibly.

"Does everybody has the perfect setup at home?"

No.

"Is this a particular problem of professional monitors?"

No.

"Are they a lot more sensitive than consumer CRT's?"

No.

"If it is due to my setup, can this be fixed? And how?"

Probably not without removing all that steel in the desk.

"Can I ground it and where should I ground it then?"

No.

"Can I e.g. make a case where I can place the monitor in?"

Possibly, but it may be totally impractical, rediculously un - cost effective and a waste of time.

"Other solutions?"

See: 1, 2, 2b & 2c in my original post.



CS

Greg Laves January 27th, 2009 09:23 PM

Simple answer: The picture tube needs to be degaused. It is a residual magnetic field in the tube that is distorting the color reproduction. If it doesn't have a "degause" control, any TV shop can do it quickly and easily and better yet, it should be fairly inexpensive.

Chris Soucy January 27th, 2009 11:10 PM

Thanks Greg..........
 
Can't imagine how I missed such an obvious suggestion.

Guess I just didn't read the thread properly.

I suppose it happens.


CS

Philip Pierloz January 28th, 2009 06:36 AM

As i said, manual degauss didn't work well. In some cases it just makes it worse. and when it finally is good, a fresh startup the day after makes it bad again.

So:
*would an external degauss by a professional work?
*why does my 15y old consumer crt work and this one not?

Already thanks for your help

Greg Laves January 28th, 2009 08:40 AM

What device are you using to manually degause the tube and what technic are you using?
I used to work at a retail outlet that had a service department. And it is my experience that if the degausing is not done properly, the result can be no change or a change for the worse. But this case has all the classic symptoms. The color shift is not a result of the CRTs current invironment. But it is affected by it. Good luck with the TV Philip.

Philip Pierloz January 28th, 2009 11:46 AM

Quote:

Originally Posted by Greg Laves (Post 1002456)
What device are you using to manually degause the tube and what technic are you using?
I used to work at a retail outlet that had a service department. And it is my experience that if the degausing is not done properly, the result can be no change or a change for the worse. But this case has all the classic symptoms. The color shift is not a result of the CRTs current invironment. But it is affected by it. Good luck with the TV Philip.

By manual degauss I mean pressing the "degauss" button on the monitor manually (like it also has been suggested) some time after startup.

What do you mean with "it's not a result of the current environment, but is affected by it" ? If something is affected by an environment, then it does have a result, not?

Greg Laves January 28th, 2009 02:35 PM

The way a old TV tech explained it to me is like this: The earths magnetic field is the culprit. Televisions typically sit in one place throughout their life. If you bought a used TV, a residual magnetic field has been disturbed and you now see the discoloration. I would call a local TV repair facility and ask them about it and find out if they can degause it for you.

Philip Pierloz February 1st, 2009 02:38 AM

An external demagnetisation didn't work. So I've contacted the supplier. He offers me the option of keeping the faulty Sony and send a second-hand JVC BM-H1400PN free of charge. I don't know this model, but it seems to have the same options of the sony. Would the JVC be a good choice? Anybody knowing this model?

Greg Laves February 2nd, 2009 12:26 AM

I am not familiar with that model but I will relate one fact. I have had 6 different Sony 8" field monitors. They always had a better picture than the 1 JVC 9" field monitor that I have. The Sony's also had more bells and whistles. But every one of the Sony's have died way too soon and the JVC is still going.

Bob Hart February 2nd, 2009 11:17 AM

There is a slight chance, if it was a custom job and not a production run which would use jigs and clamps, that the steel frame of your table was assembled using magnetic clamps to hold the corners at 90 degrees for welding.

The steel itself may have become permanently magnetised near the corner welds or even near the welds at ends of any brace bars through being heated and cooled with the magnetic clamps in place.

You'll find out soon enough by having a clamber underneath and seeing if anything steel like dressmaking pins or paperclips will cling to the barwork in corners near the welds from the corner to about 3 inches along. If they do, this may be a source for your problem.

Check for that first. If the frame itself is magnetised, we'll have to devise a means of demagnetising it.

A chrome moly airframe can become magnetised enough to throw a compass off. I imagine a CRT tube would require a stronger magnetic field to give it a problem but who knows.

The only other thing I can think of it that somebody might have dropped a pin, removed staple, paper clip, hair clip or something iron which can be magnetised through ventilating slots and it may be sitting on the coil at back of the tube itself being magnetised by the tube coils.

It might be worthwhile, if the steel frame on your work bench is not magnetised, to pick up your monitor and gently turn it upside-down by tilting it forwards.

If you hear something come off and rattle inside, it might be worth a look by a repairman. Don't go inside it yourself. A CRT monitor or CRT TV, even if it has been switched off, can give you a massive shock and release your soul.


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