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Registered Member #152
Joined: Sun Feb 12 2006, 03:36PM
Location: Czech Rep.
Posts: 3384
I know the construction of a Trinitron CRT, that's why I said shadow mask wires (a standard CRT has no wires, just a "mesh"). So theoretically it should be more immune to this kind of abuse, but I guess it can get damaged too. Or maybe the frame onto which the wires are attached got bent...
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I've made some progress with this.
As I said earlier, I've just moved house and everything is still pretty chaotic, but I've now found one of my neodymium magnets and I've tried placing it near the affected corners.
This DOES correct the problem. I have to reverse the orientation of the magnet (north fixes one side, south the other, but I don't yet know which is which). once I locate some more neodymium magnets I should be able to fix one to each side, and I'll once again have a perfect picture.
I've not yet opened up the TV, but I assume I may find some dislodged magnets inside.
The optimum position for the magnet seems to be ~6" from the corners, diagonally.
I'm not planning on opening it up at the moment, I'll just try fixing a couple of magnets in the appropriate positions for now.
I'll report on progress once I locate another neodymium magnet.
Registered Member #3271
Joined: Mon Oct 04 2010, 02:29AM
Location: Canada
Posts: 159
From my previous post: "Finally a shock could have dislodged one of the many small magnets glued on the CRT back glass. These are for corner correction mostly. It will be visible from the glue trace on the glass and loose in the insides."
I would open the TV and not power it again until you check out the scenario. Having a loose coil or yoke assemply is ok but if you have a dislodged magnet(s) it likely fell on the main pc board and could cause a short and ruin the wole set.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
richnormand wrote ...
I would open the TV and not power it again until you check out the scenario. Having a loose coil or yoke assemply is ok but if you have a dislodged magnet(s) it likely fell on the main pc board and could cause a short and ruin the wole set.
Thanks for the tip, Rich. That sounds like a very sensible plan.
It seems ok at the moment, but I will turn it off and check it now (I'll discharge the tube first, before poking around inside).
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
I think this double post is within the rules as it contains new information (I'm sure someone will inform me if I'm mistaken).
I've opened the TV and the only thing I found that was 'out of place' was a coil (maybe a degaussing coil?) around the neck of the tube, which had come out of one of it's retaining clips (see photo). I clipped it back in, but it made no difference to the picture.
Nothing else seemed amiss, nothing was loose or missing, etc. so I'll have to wait until I locate another neodymium magnet (I've found one) and correct the picture that way, unless anyone has any other tips.
Registered Member #607
Joined: Tue Mar 27 2007, 10:39AM
Location:
Posts: 64
From your temporary fix, I'll still say (along with others) purity magnets, corner correction magnets or ion trap magnets (if they exist on this newer type of tube.)
If it has ion trap (generally for improving brightness/contrast) magnets, be sure you "know" they've moved. If not and you move them, you'll cause more headaches and shorten the CRT life considerably due to ion burn.
Registered Member #3414
Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245
9.50 wrote ...
From your temporary fix, I'll still say (along with others) purity magnets, corner correction magnets or ion trap magnets (if they exist on this newer type of tube.)
If it has ion trap (generally for improving brightness/contrast) magnets, be sure you "know" they've moved. If not and you move them, you'll cause more headaches and shorten the CRT life considerably due to ion burn.
Cheers.
I realise I shouldn't have to add external magnets to correct the colour, and that this fix is indicative of a 'deeper' problem, but I'm certain that no magnets are loose/dislodged inside the cabinet.
As I previously stated, the TV only cost me £30, and I'm quite happy to replace it with another cheap one from Ebay and strip it for 'goodies', however I was quite disappointed with the size of the 'puny' flyback when I opened it up. I was expecting a TV of this size to have a larger one, and some hefty capacitors, transistors, etc. There are a few ~2 Amp diodes, though, and plenty of magnet wire around the yoke, though.
Having said that, though, IF I can 'sort out' the original problem without spending too much time and money, that will save me having to replace it if I do damage it further, as there isn't that much useful stuff inside it anyway.
Where are the magnets that you mention likely to be, as the only ones I've found are three 'correction' magnets stuck to the back of the tube?
Registered Member #607
Joined: Tue Mar 27 2007, 10:39AM
Location:
Posts: 64
The Ion Trap magnets are 3 or more thin ring magnets on the CRT neck, behind the deflection coils. Newer tubes may not have them as they may be built into the coils themselves? Be sure they've moved... If not and you move them, you can get more problems.
I've also seen correction magnets on the "fat" side of the deflection coils rather than on the bulb of the CRT.
As stated before, I'm not a TV engineer, but have dealt with purity and correction issues in the past involving all of the above.
Registered Member #3271
Joined: Mon Oct 04 2010, 02:29AM
Location: Canada
Posts: 159
Ash Small wrote ...
I think this double post is within the rules as it contains new information (I'm sure someone will inform me if I'm mistaken).
I've opened the TV and the only thing I found that was 'out of place' was a coil (maybe a degaussing coil?) around the neck of the tube, which had come out of one of it's retaining clips (see photo). I clipped it back in, but it made no difference to the picture.
Nothing else seemed amiss, nothing was loose or missing, etc. so I'll have to wait until I locate another neodymium magnet (I've found one) and correct the picture that way, unless anyone has any other tips.
Ok. Included are two photos of the back of a 32" Sony Trinitron.
You can see near the neck the round magnet being held by a double sided tape against the back of the CRT. There is another one hidden by the electrostatic/blast shield where the yellow circle is. You need a small flashlight to see it.
Second photo is the other side. Same configuration.
The bottom half did have a magnet near each corner and one other in the middle. None near the neck.
The pattern is slightly different for each set or model. The sticky tape is old and it is easy to pry the magnet off (which leave an indication the its location) or the tape off the glass. The ones under the shield would get caught inside it.
Also note the yoke being help in place with one clamp and four rubber wedges that are also glued to the back of the CRT. It could be off position too.
If you do not find any of these loose (degaus coil is not an issue) I would follow the SONY purity adjustment procedure (usually involve pure red screen and pulling the yoke and repositioning it. Resist the temtation of messing around with the convergence adjustments.
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Wierd colours on my TV?
