Help me I.D. and degauss this 29" flatscreen

[IntruderAlert]

Anybody recognise this monitor?
It's a 29" flatscreen

There is some discoloring in the bottom left and top right corners
Can this be fixed?
I guess I'll need to degauss but I don't know if it has a built in degauss switch or not

I'd really like a manual or any info you guys can provide

[DaveJ-UK]

Are there no markings on the PCB?

I had similar issues with a WG monitor of mine, which turned out to have 2 unshielded speakers in the cab. Try removing the speakers as that would be a very easy fix.

[MonitorGuru]

As far as I can see, there is NO degaussing coil wrapped around the tube or attached to the board.  Most monitors auto-degauss when they are powered up and unless it's really bad you don't need to do anything.

however this one is lacking it anyway, so you're going to have to degauss it yourself.

The problem may be earth related. Try twisting the cabinet 90 or 180 degrees. Do the colors go away or turn to purple instead?

Or they may be speaker/power supply related. Do you have an unshielded speaker in the upper right of the cabinet and a power supply in the lower left?

Or it could just have had the shadow mask magnetized by being in a cabinet with unshielded speakers before.


In any of these cases, you will probably need to degauss the tube manually. Just build or buy a degaussing coil, or at the very least try a powerful soldering iron to use as a quick degausser and see if that helps.

[cholin]

Can you guys explain how this degaussing stuff works?  What does it do?  How do you do it?  Ive heard alot about it, but never understood it.

[MonitorGuru]

Use search... 5 pages (* ~40 posts per page) of results on Degauss.

In summary: A degusser produces an alternating current wave in a circle of wire.  This current helps remove magnetism that is stuck on metal objects such as screws, monitor frame, and the shadow mask inside the tube itself.

You start with the circle against the monitor then make concentric circles around the monitor while slowly moving away from the monitor. Once you are about 6 feet away from it, it should no longer be bending/discoloring the picture and then and only then do you turn it off. If you turn it off against it, you can remagnetize it and have to do it again.

It's safe to do while the game is on and helps determine where you need to do it more/longer.


All monitors and TV's are supposed to come with a wire around the back outside of the tube that sends about a 3 second jolt of AC power through it when the set it turned on.  Otherwise, your TV would eventually become discolored or other problems if you moved it through the house or even just let it set  due to the earth's magnetic fields.

[IntruderAlert]

will this procedure cause me to become radioactive and/or destroy my reproductive abilities ?

... could i build my own degaussing coil around the tube so that i can press a button to degauss when necessary?

[MonitorGuru]

>"Will I become radioactive"

No.   A degaussing coil is essentially 1 side of a transformer, just missing the iron core and the opposing winding.

It creates a localized strong magnetic field, so you wouldn't want to place it around your head and wear it around the house, nor of course, seriously, use it if you have an electronic medical device implanted in you (like pacemaker or insulin pump, or metal plate in your head, etc...) 

There is no chance of radiation, just an alternating magnetic field.


The chassis problably already has a deguassing coil connection.. Just steal a coil/pair of coils from another TV/monitor and use them.  However the power on degaussing is not as effective as doing a thorough degauss yourself with an external loop.  The power on one is intended to remove small imperfections each time it's turned on.  If it's really bad it may take a lot of applications to get it to clear it, versus using an external loop.

[IntruderAlert]

ok.. thanks

so i should just build one of these then?
http://www.oscarcontrols.com/degauss/index.shtml

or do you know a better way?

and since you're the MonitorGuru and all.. i've always wondered why CRTs whine while they are warming up and some of them seem to continue to whine even after they warm up

[MonitorGuru]

I would do Oscar's hack, however to make it easier, just steal the loop from the insides of a dead computer monitor or TV set. That saves you most of the time. You still need to put an AC wire, light bulb socket, light bulb and switch on it of course, but that's the easier part.

Alternately you can try to just use a ~150 watt gun shaped dual post soldering iron. They produce a pretty strong alternating magnetic field (but in a smaller area) . They're $5.99 on sale at Harbor Frieght a lot of the time. .. just don't accidentially touch the hot tip to any of your cabinet or yourself while you use it!


As far as whining... common problems are:
- Old monitor
- Drying out capacitors, especially the large filter capacitor
- A transformer that has the outer sheild broken from the core (though more of a buzzing sound but can be whiney on the high frequency switch-mode style ones)
- An anode cap that isn't fully on or attached to a very dirty tube..this however normally produces arcing (blue light) and crackling and shrinks the picture each time it does.
- A crack in the flyback transformer housing and/or the iron core has broken free from the housing and is vibrating.


Take your pick... you have to narrow down the location of the problem to know more specifically which one of the above it could be.

[IntruderAlert]

hey.. i've got one of those bulk video erasers lying around
can i use that?

..and I ALWAYS hear CRTs whine.. every last one of them

[MonitorGuru]

Yes... a one of those square (palm sander sized) bulk tape erasers will work pretty well... probably as good as the soldering iron.

Oh, if you mean normal whine, then what you're hearing is the 15.75 KHz sweep of the electron beam due to the horizontal deflection of the yoke.

[IntruderAlert]

mine's like this one:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=14968&item=5761110417



mine has no name on it but this ad says

Magnetic flux: (Open field) 1600 gauss at 1/4 inch. Max current: 12A.

but if there's a chance of messing up something I'll just build or buy a real one

[IntruderAlert]

OK.. i've been tracing down the wiring problems in the machine and I have it working again.
I discovered a control panel for the monitor controls hidden behind one of the light panels but there was no degauss selection in the menu.



I also discovered these pins on the monitor board labeled "D-COIL"
I don't know if this is where you would attach a degauss coil or the switch for one or what.



there's also these controls for focus, screen and something else


I got a closer shot of the sticker on the side of the monitor



as you can see it says A68QCU259X which is the code for the tube only and doesn't really tell the whole story of the monitor

I found this link and this link which show monitors using this tube at 800x600 and 1024x768

i also found this link which shows a monitor using this tube at 640 X 480 (800 X600 Option)

so i still don't really know the resolution of this monitor
but i'm guessing that it's not going to be good for standard resolution

[IntruderAlert]

I went ahead and zapped the monitor a few rounds with my bulk tape eraser and it got rid of about 95% of the discoloration
barely even noticeable by me because I know what I'm looking for.
I'm guessing that most others wouldn't notice a thing.

now how about switching this baby over to 110v ?
would I just need a different flyback transformer or what?

[DaveJ-UK]

You wouldn't need to change the flyback, just the isolation transformer I _think_ but wait for Ken or Monitor Guru to comment.