basic TV question

Do all TV's have built in degaussing coils these days?

I have a CRT style TV that's been in service for ~ 4 years and it has been gradually losing "color purity" mostly on the bottom edges in a circular pattern - center good.

I can null out the green or magenta it favors and correct the color by holding a piece of non-magnetized iron in just the right place in front of the screen, one corner at a time, so I'm fairly sure it is a problem with a magnetized chassis or color mask.

I've never heard a 60 cycle buzz when the set fires up the way normal degaussing circuits sound, but didn't think anything of it until the purity started to go out. Could I have skated this long without a problem with no built-in coil? And can they make them totally silent?

Plan A is to whip up a manual degaussing coil. I have 5,000 feet of

24 AWG and figure 3,000 feet on a 14" diameter coil will have a reasonable impedance and use ~60 watts.

Plan B is to fix the set

Reply to
default
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My tv, and my 7 crt's give a nice "boing" when swithed on, so there must be something wrong with your tv. There sould be a coil around the front of the tube, and a relay and ptc resistor to let the current trough that coil fade away to zero. That somewhat de-gauses your screen. But only if it works. Very big errors need an external paddle de-gauser.

Reply to
Sjouke Burry

"default"

** All colour TVs and monitors that use CRTs have them.

It's essential.

** Most degaussing coils make a bit of noise when the screen is switched on - but some may be very nearly silent.

Your problem is that the PTC thermistor circuit that drives the coil has failed.

May be because of the PTC device itself, a blown fuse or a bad connection to the coil.

.... Phil

Reply to
Phil Allison

Do you have a soldering gun? They are good degaussers.

John

Reply to
John Larkin

Thanks

I do, and tried that. Winding a coil and connecting it in place of the tip may be a winner. The gun alone, with a regular soldering tip, tried in all orientations, did help - the side bands are almost gone and the center (where I didn't think there was a problem) looks better.

But there are still two pesky areas on the bottom corners. If I didn't know better, I'd be looking for a hidden magnet.

Reply to
default

Just fix the TV.

Reply to
Tom Biasi

I never thought of that, I was cobbing something together the other day to demagnetize some tweezers.

George H.

Reply to
George Herold

Do you have kids? "Hidden magnet" just made me think of that for some reason.

Just fix the dang thing.

--
Tim Wescott
Control system and signal processing consulting
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Reply to
Tim Wescott

Hmm, could they be due to the speakers in the set itself, or a nearby stereo?

Best regards,

Bob Masta DAQARTA v5.10 Data AcQuisition And Real-Time Analysis

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Reply to
Bob Masta

Now where's the fun in that? It is a big beast and I don't want to move it.

Calculating the inductance for a degausser is more rewarding than poking about in TVs.

Reply to
default

No kids or magnets that I see. Speakers inside the set have magnets no doubt.

Fixing is a less desirable option. Ages ago I repaired TVs for a living. Good chance that if it needs any part it will have to be ordered, since there are no parts outlets around here. It is a large beast. Could just be a fuse . . .

Reply to
default

a
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We had a cheapy Daewoo set for the kids where the degausser failed. It has a relay on the main board that flexes the contacts slightly when it actuates. The solder joint eventually failed and all it took to restore it was to clean off the remaining solder and re-solder it. Works fine again.

G=B2

Reply to
stratus46

default schrieb:

unlikely, PTC is more likely.

Some time ago, I had a similar problem: Built in degaussing didn´t work and the PTC sat inaccessible below the very large CRT (>30"). I took the degaussing coil and circuitry (which was fortunately on a seperate print) from an old set set, which was scrapped at this time. I held the coil in front of the TV and moved it away slowly, the way it was done before built-in degaussing was standard (prior to ~1960) (I know this from american literature only, the first color-TVs in central europe allready hat built-in degaussing (~1967)

greetings, Rudolf

Reply to
Rudolf.Zeitschek

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