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Naomi CRT Swap issue

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ID4:
Hi folks!

I have one Sega Naomi Cabinet, the original Toshiba Tube (A68KJU96X) was very damaged, so I swapped the original 29' Toshiba tube for a 29' Philips one (A68ESF002X11 borrowed from a tv).

The Philips tube is mounted *USING* the Toshuba tube original yoke, so the Philips tube is working with the chassis Nanao MS-2934.

Notice that unlike the Toshiba one, the Philips tube don't have magnetic rings, it has the magnetic adjustments made in the factory, inside the electron gun.



The image quality is really amazing, the problem is that I newer get the color purity fixed and always have blue magnetic spots at right corners

I have tried the demagnetizer of the cabinet, it removes something but the spots come out again instantly.



Using the corrrect orientation, I've tried adjusting the yoke by moving it along the neck of the tube, rotating it, tilting it to either side, etc.

Notice that if I move the yoke all the way back, the circle that appears on the screen is moved to the left, I suspect that is the problem.



How I can I fix this? If needed I can add the magnetic rings from another tube to this one, I tried to adjust the chassis but no result.

Thanks in advance!.

lilshawn:
typically there are chevron shaped magnets attached all over in mas produced tv tubes used to help get things lined up better.

that said... it looks like it's a simple degauss issue here. the purity is good except for some areas in the corner, you usually have to degauss the screen, as the frame of the arcade monitor usually has some pretty hefty magnetic fields stored in it over the years. the old tube would be already degaussed to this metal being so near it.

your TV tube was sitting in a plastic case with no metal around it when it was setup and degaussed so you'll need to degauss this new tube so it's in sync with the magnetic fields all around it now.

ID4:

--- Quote from: lilshawn on May 05, 2022, 01:15:18 pm ---typically there are chevron shaped magnets attached all over in mas produced tv tubes used to help get things lined up better.

that said... it looks like it's a simple degauss issue here. the purity is good except for some areas in the corner, you usually have to degauss the screen, as the frame of the arcade monitor usually has some pretty hefty magnetic fields stored in it over the years. the old tube would be already degaussed to this metal being so near it.

your TV tube was sitting in a plastic case with no metal around it when it was setup and degaussed so you'll need to degauss this new tube so it's in sync with the magnetic fields all around it now.

--- End quote ---

Thanks you for you reply! I have already used the degauss button of the machine, the screen "jumps" and the spots disappear but reappear immediately.

Maybe did you refer to other method? Then how effectively demagnetize the tube?

I have googled and found that this Philips tube originally the magnetic rings are included in the yoke, so when I removed the yoke and plugged the Toshiba one, I left the tube without magnetic rings, than can be the cause.

If not, why if I move the yoke all the way back, the circle that appears on the screen is moved to the left?

Thanks !  ;)

lilshawn:

--- Quote from: ID4 on May 06, 2022, 02:13:43 am ---If not, why if I move the yoke all the way back, the circle that appears on the screen is moved to the left?

--- End quote ---

because you are affecting the election beam before it has a chance to begin accelerating from the guns. you are probably deflecting particles or making them emit from someplace they aren't supposed to by yanking them out with the magnetic field from the yoke.

the degauss coil on the outside of the tube is good enough to remove a small residual field, but not powerful enough to realign it. you will need to buy/borrow/steal/pay someone to do it with a specific device. you can buy cheapy ones off ebay for like 20 bucks... i dont know how good those are. probably worth a try though. i have a huge industrial type degauss coil (about 14 inches in diameter) for doing CRT's.

https://www.ebay.ca/itm/393969713049?_trkparms=amclksrc%3DITM%26aid%3D1110006%26algo%3DHOMESPLICE.SIM%26ao%3D1%26asc%3D20200818143230%26meid%3Dcf59e465cdf44a3bb58156e13c270003%26pid%3D101224%26rk%3D3%26rkt%3D5%26sd%3D165009205054%26itm%3D393969713049%26pmt%3D0%26noa%3D1%26pg%3D2047675%26algv%3DDefaultOrganicWeb&_trksid=p2047675.c101224.m-1

plug it in, power on the monitor... move in close to the front of the screen, turn it on an wave it around in a circle around the outside of the face as you move  backwards... 1 circle..move back a little...one more...move back... till you are hardly affecting the screen...youll be about 2 or 3 feet away then turn it off.

Zebidee:
I have a couple of those cheap degaussing wands and they work fine.

Word of warning - don't operate them continuously for more than about 10 seconds or so. They will get quite warm and if you leave it on it will start to melt the casing.

If that doesn't work, it may be possible that you need to use some color purity rings with that philips tube/toshiba yoke combo.

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