CRT monitor, shadow across bottom quarter (sometimes top), repair or junk?

Question

I have a monitor, a 21" CRT monster, that I just LOVE. Recently it has begun to develop a shadow across the bottom quarter of the screen after its been on a bit, sometimes the top as well. I specifiy 'shadow' instead of 'black' because those sections of the monitor don't become impossible to see, its just like they are literally in a dark shadow, you can read through it.

Ive noticed that giving it a good shake or an emotionally satisfying whack on the side makes it temporarily go away, but it always comes back.

What is this shadow caused by? I have a practically non-existant budget so if repair is an option I would like to pursue that, but I know monitor repair is a tricky thing. I am aware certain parts going bad (ie the cathode) make it cheaper to buy a new monitor, but the symptoms make me think this is not that, I just don't know what it is.

Any monitor-wise folks familiar with this shadow effect that can advise? Tossing it is a last resort for me, if even an option

Thanks!

Answer 1

Firstly, it's not a screen burn. Screen burn is actually the phosphors getting worn out due to a constant image being placed on the same location. You often see it in bank auto-teller machines. It may even be visible when the monitor is turned off. If it appears as the monitor is warming up, it's not that.

Degaussing is used where the shadow mask has got magnetised. The effect of this is to give the screen and out of focus effect or colour fringing, the same as if a magnet is put near the screen (don't try this with a super magnet- you'll probably need a powerful professional degausser to get rid of it- you have been warned!).
BEFORE GOING INSIDE READ BIT FIRST:
There are a lot of nasty voltages in a CRT and turning it off does not get rid of them. The EHT will be at a lot of kilovolts and it'll do more than give you a little shock- IT CAN KILL YOU! Don't go inside the back unless you know what you're doing and don't touch anything unless you are confident you know what it is you're touching. If you're not sure, either get it repaired or buy a new one. A new 19in LCD monitor is almost the same visual size as an old 21in CRT and a lot less heavy and a lot less power hungry and probably just as good unless you're a stickler for colour fidelity. Really now only fastidious designers need 221 inch CRTs and your old monitor sounds knackered anyway.

So what is it? The bang on the side is the giveaway. Inside you've probably got one of the following:
1) You have got a dry joint - which is either a bad soldered joint or one which through time has become corroded. This can be fixed easily by re-soldering it- but (isn't there always a but!) you need to know where it is first.
2) A connector or lead has become corroded or slightly loose or oxidised. I had a TV that was a pain for this. One connector would keep dying every 6 months or so. I'd unplug it and plug it back and it worked again quite happily for another 6 months. I never fixed it properly because every time you removed it if fixed itself so I could never actually find the fault.
3) A component is failing but not yet full dead.

All of the above can appear the monitor is warning up due to the thermal expansion of whatever is failing. Sometimes it only when it fails fully that you'll be able to fault find it as taking the back off will cause it to mysteriously fix itself!

You could go inside (see the previous warning!!) and unplug and replug every connector and use some WD40 on every bit. You could also hoover out the inside- it's probably attracted a load of dead spiders and dust. Some will need wiping off with a slightly damp cloth- but again the dirt will congregate around the EHT (ie deadly!!) bits.

Go green, splash out on a new LCD monitor and save the planet!

Answer 2

The CRT retains a deadly charge even after it's been turned off, unplugged, and stored in a box for 3 weeks. Really. I've done the discharge procedure on monitors that have been unplugged for weeks, and gotten a hell of a spark. Unless you really know what you're doing (in which case you would not be asking about hazard), it's very unlikely that you could fix it. Write it off, buy a flat screen, never look back.

Answer 3

If you have a DEGAUSS button you can try that to see if it has any effect. If no change then junk it. Unless you need a CRT, I would recommend a 21" Flat panel, less room on the desk and less energy used. Plus the picture looks so much nicer. Good luck.

Answer 4

I would have to agree with the previous answerer. With a non-existent budget, I would also suggest a VGA LCD monitor, or you could even go to a digital LCD monitor. The digital will give you better picture, but some computer don't have a digital output. Check woth your instruction manual to see if a digital is right for you.

Answer 5

You COULD be suffering screen burn, wrecking your poor monitor. Screen savers prevent but do not fix it.

Answer 6

junk