K7000a - Apparent bad purity between multiple tubes

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Hello ya'll just curious if anyone come across this.

I have a troublesome k7000a that I've been unable to get a decent picture from. I've run it with multiple tubes, recently with a brand new (to me) Magnavox 25" tube swap.

Picture has colors scrambled (R to B, G to R and B to G) with what looks like bad purity.

I've had sucess completely resetting the yoke and purity rings before (I know it sucks) but with this tube an chassis, following the k7000 manual, I can't get the thing to display solid green, no matter how close the yoke sits, or how high/apart I adjust the purity rings.

I've run this with a TPG so I know its not wiring. And I've tried degausing the monitor several times over several days.

And since I've seen this issue on different tubes my thought is that it's the chassis, though I've not seen anything about chassis issues causing this symptom, only degaus/purity/yoke issues. I've watched just about every k7000 video on Mikes youtube channel. Shout out Mike!

I've also tried my recent tube with a different yoke and have the same symptoms.

Anyone have any ideas why a board would have these symptoms??

The images show Diehard with mixed up colors, and TPG with bars, I'm not sure why red is missing but note blue is first, green isn't in the middle so picture isn't fliped.
 

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Is this a new, to you, chassis?
If so, I would suspect a problem with the wiring between the neck board and the chassis. Looking at the datasheet for IC1, I don't immediately see how the color signals could become mixed up in there, but strange things do happen.
One possibility is a solder splash between a couple of pins of the RGB input connector on the chassis or the transistors or components in that circuit.
If you have, or have access to, an oscilloscope, try this:
- Turn off the green and blue output from your TPG
- Check the red signal at the output of the TPG and at pin 8 of the CRT socket. The output of the TPG should be about 1Vp-p, and pin 8 of the CRT should be about 10vp-p. There should be no signal on pins 6 (green) or 11 (blue) of the CRT.
Without an o'scope, input an RGB signal and measure the voltages on the neck board transistors and, if not correct, check voltages on the input and output of IC1 and the voltages on Q1, Q2, and Q3. Those voltages are listed in the K7000 manual.

If this is a problem that suddenly appeared in a working chassis, I would still start with an o'scope to try to see what is happening where.
I believe that the purity problem is separate issue. Best to get all the colors displaying first. Purity won't matter until the colors are correct.
 
Im not understanding here I think, has this chassis ever tested good on a known working decent condition k7000, u2000, u5000, k7400, hantarex polo, or neotec std res tube?IE those other tubes were tested with a good one of those chassis and they worked fine? Because this makes me kinda think from your original post that you do not really know if those tubes have issues as well?

Idk if this is the case or not but testing and unknown chassis with an unknown tube opens the door to like a million potential problems lol

I guess you said you had a good picture before with that chassis, then you put this chassis back on the tube with out messing with its yoke and convergence rings and now this is happening?
 
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Thanks for the help ya'll

To clarify, I have all 3 colors, they're just mixed up, and rainbowing together like a bad purity issue. I'll def try a different neck board, assuming k7000/k7000a are compatible. Noticed my k7000a neckboard has that looking coil around the flyback mod. I'm having trouble remembering what that is about.

It is a "new to me" chassis that I've always struggled to get a decent picture on. I'm in a land were getting my hands on a 100% known good tubes/chassis is difficult. It took me 2.5 years of sluthing to source this 25" tube...

Anyways, Maybe I'll try this tube in another game too to make sure its not completely wonky.
 

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Noticed my k7000a neckboard has that looking coil around the flyback mod.
What coil looking thing? All K7000 neck boards are interchangeable. Post a picture of your chassis and neck board.

So now I'm confused. Are you saying you bought this chassis "new to you" as working, but you never actually seen it working correctly?

Are the signal wiring in your cabinet or tpg correct?

Unless I'm wrong. I wouldn't be messing around with the yoke and rings worrying about convergence and purity right now. Could this cause your color bars to be in the wrong position while using your tpg? I doubt it. I've never seen it.
 
What coil looking thing? All K7000 neck boards are interchangeable. Post a picture of your chassis and neck board.

So now I'm confused. Are you saying you bought this chassis "new to you" as working, but you never actually seen it working correctly?

Are the signal wiring in your cabinet or tpg correct?

Unless I'm wrong. I wouldn't be messing around with the yoke and rings worrying about convergence and purity right now. Could this cause your color bars to be in the wrong position while using your tpg? I doubt it. I've never seen it.
I wonder if it's secondary winding heater mod for use with shorted electron gun tubes. it's a mod I've done several times.

if that's the case it's a wire wrapped around the flyback core? it will work with any tube, it'll just be generating the heater voltage using mere physics instead of the actual voltage tap through ground. it's just kind of cumbersome to handle. ask me how I know. ;)

some tubes have different pinouts for the RGB at the CRT neck. that's definitely a purity issue in the 2nd picture at the top, but purity is not handled at the deflection board, it's the first ring pair at the ring assembly around the glass neck.
 
I wonder if it's secondary winding heater mod for use with shorted electron gun tubes. it's a mod I've done several times.

Yes I believe this is the mod. I'll post a pic next time I am able. Soo.. call me crazy, but if my new donor tube doesn't have shorted guns...could I be pushing too much voltage through them causing apparent bad purity?

To be clear, I've already adjusted the yoke and purity rings to the best of my knowledge, and can't get a better image than shown.
 
Yes I believe this is the mod. I'll post a pic next time I am able. Soo.. call me crazy, but if my new donor tube doesn't have shorted guns...could I be pushing too much voltage through them causing apparent bad purity?

To be clear, I've already adjusted the yoke and purity rings to the best of my knowledge, and can't get a better image than shown.
no, I already said the deflection board has nothing to do with purity. you said you did a tube swap, there's a possibility you either have the yoke or ring assembly or both positioned wrong. this is why I keep saying if you lack jedi training you shouldn't be doing tube swaps. that's like one of the last things you should learn how to do.

also the secondary winding mod I've done by the book and it usually comes out to less than 6.3V to the heater.
 
I'll get the tube on a known good chassis and see what I can see. If we assume a mere mortal such as myself has the purity and yoke setup correctly, is there anything else I can look at? Or is it just incompatible tube at that point
 
I'll get the tube on a known good chassis and see what I can see. If we assume a mere mortal such as myself has the purity and yoke setup correctly, is there anything else I can look at? Or is it just incompatible tube at that point
No the convergence rings can have an impact on it as well, the two closest to the yoke also deal with purity issues, and ive seen them have a huge impact on purity issues at times. The others deal with linearity. So do not mess with those and always mark the rings in a couple spots before messing with them. Also how close or how far the rings are to the yoke can also effect purity in some ways.
 
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