My CRO is acting up. When you move a trace to the top of the screen, the trace angles upward, and when it's at the bottom it's angled down. This happened since I temporarily placed a small laser printer on top of it and made a couple of prints, in hindsight probably not the best idea. I supposed something has gotten magnetised. Is it possible to fix this?
you've played with astigmatism, rotation, intensity etc to no avail?
CRT's are electrostatic if I remember correctly although still affected by magnetism. Wouldn't expect a degauss function.
What model? how old?
If it's a single channel why worry. It's probably a dual right?
CRT's are electrostatic if I remember correctly although still affected by magnetism. Wouldn't expect a degauss function.
What model? how old?
If it's a single channel why worry. It's probably a dual right?
It seems plausible that the shielding around the CRT was magnetized by some current pulse in the printer, but I stack all sorts of test equipment on my scope, and have never had the slightest problem. So have a lot of other people over the decades. Can you describe the scope- is the enclosure metal? If something got magnetized, it should be possible to demag it using an old TV degaussing coil, but I'm betting something else happened.
All 'scopes use CRT's with electrostatic deflection. There is usually a magnetic shield around the CRT to minimize interference from external B fields. It sounds like this got magnetized. Get a bulk tape eraser and try demagnetizing the shield around the CRT.
WARNING! Do not try this trick with a video display. A video display uses magnetic deflection coils. They usually have permanent magnets attached near the CRT to compensate for (cancel) the earth's magnetic field. If you try to de-gauss the shielding around a video display, you will probably demagnetize the permanent magnets and screw it up.
WARNING! Do not try this trick with a video display. A video display uses magnetic deflection coils. They usually have permanent magnets attached near the CRT to compensate for (cancel) the earth's magnetic field. If you try to de-gauss the shielding around a video display, you will probably demagnetize the permanent magnets and screw it up.
It's an LG-9020G 20Mhz scope.
I havn't tried the rotation control yet but it was perfect before this happened.
I have some 6v mains toroids. If I make a coil of wire around an old file or screw driver, will this make an adequate degaussing wand? (Powered by the toroid)
I havn't tried the rotation control yet but it was perfect before this happened.
I have some 6v mains toroids. If I make a coil of wire around an old file or screw driver, will this make an adequate degaussing wand? (Powered by the toroid)
Hah! I had a reel of speaker cable, the complete reel measuring about 5ohms DCR, so I put 6vac across it, waved it by the scope a bit and slowly pulled it away and it worked! Woo, nice straight traces again!
I think the steel case must've been magnetized
I think the steel case must've been magnetized
Charles Hansen said:
Most of the "unwanted" magnetism on TVs is not in the coil region but the shadow mask or the fixings round the screen.
I never had any problems in over 12 years
Andy
poynton said:
Good for you. In the meantime:
http://www.laserfaq.org/samnew/tvfaq/tvdegacrt.htm
"WARNING: Don't attempt to degauss inside or in the back of the set (near the CRT neck. This can demagnetize the relatively weak purity and convergence magnets which may turn a simple repair into a feature length extravaganza!"
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