Tube swap: messed up colors

TheShanMan

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I am in the midst of my first tube swap. The chassis is in the k4900 series I believe (although I couldn't find the exact number) and the tube came out of a tv I picked up. It looks extremely gaussed to me, although my degaussing coil didn't seem to make a big difference. I made the mistake of not checking the picture quality of the tv first so it's possible that the tube was like this in the tv (I will put it back and check if needed).

However, I'm hoping the problem will be obvious to someone here and the solution simple. :)

Granted, the chassis needs a cap kit (which is next on the agenda), but the old tube didn't have this kind of color problem.

So what's causing all the green, and the little bit of blue, on a screen that's supposed to be nothing but red?

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for starters is the yoke all the way up on the tube? If so then my next thought is it needs a magnet or two to even out the color. You know the real thin magnets that are present between the yoke and tube on some monitors. Remember that tube was adjusted and working to match the yoke and chassis it had not the one you put on it. So it needs adjusting to work and look good with the components you swapped in. Tube swaps often go easily but they are not always plug and play/swap and go.. whatever.
 
Yes, the yoke is all the way up, although I haven't yet pulled off the rubber stoppers to have more room to play with adjustments.

Those magnets are for convergence. I don't think they'd affect this, would they???
 
tube swap

Did you mark on the position of the yoke and the purity magnets on the original tubes the TV tube and the WG?
Did you try to use the Yoke and purity magnets from the tv or replace them with the WGs.
Did you measure the ohms on the H and V deflection.

Are the 3 ruber feet installed?

Is the yoke centered. Has the tube been rejuved?

RJ
 
Like I said, I haven't removed the rubber stoppers (feet) yet. Rings stayed with the tube, yoke with the chassis. Rings were marked and returned to the original spot.

I did not realize that measuring the ohms was a necessary step to be honest. I thought 19", cr-23, and I'm good to go. Guess it's more than that.

I haven't rejuved yet. I had no idea that a tube needing a rejuve could cause a picture like that though.
 
so if your rings are from the tv, yoke from you orig chassis it sounds like your yoke is out of position. those rubber wedges were for the original yoke from the tv. keep moving the yoke around until your screen is completely red. once your screen is completely red then the wedges go in to support its position and then lock the yoke down but do not over tighten or you can crack the tube.
 
Yes, the yoke is all the way up, although I haven't yet pulled off the rubber stoppers to have more room to play with adjustments.

Those magnets are for convergence. I don't think they'd affect this, would they???

The rubber stoppers were for the other tube. They are just spacers to keep the yoke at a correct distance from the tube to make the picture correct. Different tube will require different adjustments and possibly even no rubber wedges. I don't know a great deal but I was always under the impression that those magnets were definitely used to correct color issues that were linked to magnetism/ degauss issues. Don't know how or if they effect convergence. Never heard that they did although I may be wrong.
 
the magnets are to dial in the edges of the screen. once you have full red. go to a cross hatch. if your rings are in the right spot you may not have to do any magnets. usually the center of the screen can be dialed in and you use the magnets to pull the edges of the monitor to where you need them.
 
Oh, they definitely affect convergence. That's exactly what I used them for on my paperboy monitor a while back. Sometimes due to manufacturing flaws you simply can not converge every part of the screen, and magnets are the only way to correct it.

I will pull out the rubber stoppers and see what happens. After that I will check impedance.

EDIT: Yep, Fudd stated it more precisely than I did.
 
It was the yoke position. Got these problems to go away. Before I continue with tube swap work (since I see that this is going to succeed), I'm going to cap the chassis because it needs it badly (or at least, I hope a cap kit will take care of it!).

Thanks guys!
 
So far so good. Cap kit really helped with the picture.

Now I'm having a bear of a time getting all of the yellow/orange off of the red test screen when moving the yoke. Move it too far one way and it appears in one area. Move it too far the other way and it appears in another. Haven't found a happy medium yet.

Anyone have tips for yoke adjustment? It's kind of a pain when you don't have the rubber bumpers already positioned properly. I'm sure I'll get it, but it seems like there must be a slightly easier way than how I'm doing it. Hmmm. I might try tightening the screw until it isn't quite so loose, yet still allows adjustment. That's probably my problem.
 
Please let us know how it goes with pics. Any tips on this would be of great help since I have a KI machine with a bad tube and a MK 2 machine that I might get if I can do a tube swap successfully on my KI machine. The MK2 machine has horrible burn. I have been looking for good tutorials on tube swaps and haven't found a good one yet that explains everything to take into account and pictures included with the process.

Thanks a lot
 
I started another thread to discuss the fact that I couldn't, for the life of me, get the green to converge with the magenta to anything close to an acceptable degree. No real solution there as of yet so I am about to judge that tube to be a bust, and move on to another tube. :(
 
I'm thinking I'm gonna spend more money on old tv's that don't work rather than buying a new monitor. I mean I can tell the guy to take the tv apart and give me the model number and check the ohms for me. Any real way to get the right tube?
 
I'm thinking I'm gonna spend more money on old tv's that don't work rather than buying a new monitor. I mean I can tell the guy to take the tv apart and give me the model number and check the ohms for me. Any real way to get the right tube?

Make sure if your arcade monitor has a cr-23 neckboard connector, that the tube you get does too. That's the main thing. I just take a printout of tube numbers and their connector with me to the local goodwill outlet with a flashlight and a couple other tools to help me peek in and see the tube #.

Did you check to make sure it's a 90 degree tube. The tube will have a number cast into the back of it. It should be 19V90

I looked but didn't see any number cast. However, I really wouldn't expect 100 vs 90 to cause ONLY the green to have the problem I described in the other thread.
 
Before you can even begin to do the convergence, you need to get the purity right. That's the solid-color-screen-with-other-colored-blotches problem. Start with the green (that gun is in the center of the assembly), then red and blue. Purity is established by using the position of the yoke and the pair of ring magnets that are closest to the yoke.

After you get the purity right (each solid colored screen only displays it's proper color, no blotches), then move on to convergence. Start in the center of the screen - use the other pairs of ring magnets to align the crosshatch in the center. Edge convergence is done with slight yoke tweaks and those little convergence strips for the corners.

-Ian
 
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