Tube swap question

racer2e

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When doing a tube swap, how close would the yoke readings need to be for you to give it a shot? I really don't want to mess with convergence.
Jayme
 
Within several ohms. I've got a newer tv tube running with a WG K7000 that had a difference of 3-4 ohms and it works fine.
 
If you take care of keeping track of where rings and magnets (if any) were when swapping, you shouldn't need to converge if you keep the original yoke. In fact, if you have the original yoke, it's better to use it if you can.

I've swapped several tubes now, and the only time I got a decent enough picture out of the TV's yoke was with a Wells Gardner 19K7xxx chassis.

My G07 and 19K49xx chassis' both required the original yoke be fitted on the donor tube. My 4900 had magnets taped to the inside of the yoke, and I made sure to re-tape them in place to preserve the correct convergence. Be careful when pulling off the old yoke - sometimes the magnets are not being held on by the tape any more b/c the tape has dried up and flaked away. As soon as you move the yoke away from the tube, the magnets will slip out and fall to the counter/floor. I was able to identify where my magnets belonged by the shiny copper squares left behind when the tape fell away. The tape prevented the copper coils from oxidizing as much where it was covering. Once I matched up the squares, re-taped the magnets down with electrical tape.

If you're courageous enough to dive in and swap tubes, you might as well go the distance and swap the yoke too.
 
Actually as I learned over time through frustrating experience and confirmation by a guy in the tube business (hawkeye), yokes are not just mated to chassis, but also to the guns in the tubes. So if you use an arcade chassis and yoke with a tv tube it is very common to not be able to get good convergence away from the center no matter how good at convergence you are. Even though you might have another CR23 tube, chances are good it has a different gun that will cause you to waste a lot of time and pull a lot of hair out trying to get it to converge.

Your best bet is to swap tubes and yokes as a unit, after confirming that the impedances are a close match. And to Jayme's original question, I have yet to get a feel for what's close and what's not. I've got a K7000 and a TV tube that I think are close matches - 2.4 vs 3.0 and 11 vs 13. If anyone with experience can tell me ahead of time if that is close enough, it may save me some wasted effort. But I plan to give it a try in the near future.

And regarding smalltown's comment about only having success with tv yokes on a k7000, I have successfully swapped a tube + bonded yoke onto a k4900. It does have slight pincushion which bugged me at first, but no one notices it and it doesn't bother me anymore. So don't take his comment to be an indication that you can't succeed with a tv yoke on a g07 or k4900.
 
I swapped both yoke and tube on a WG K7200 and it turned out perfectly. I had the wrong remote board at first which caused some issues with skew and trapezoiding, but once the right remote board was installed, I have had zero issues and the picture is stunning. I had to do zero converging. I used a 19 inch Daewoo tube.
 
So if you use an arcade chassis and yoke with a tv tube it is very common to not be able to get good convergence away from the center no matter how good at convergence you are. Even though you might have another CR23 tube, chances are good it has a different gun that will cause you to waste a lot of time and pull a lot of hair out trying to get it to converge.

I've never heard this, but it makes sense. I have thrown out good TV tubes because I couldn't converge them (no even close) on an arcade chassis. Even the tubes that do work better are very hard to get looking good and a compromise has to be made somewhere.
 
I've got a K7000 and a TV tube that I think are close matches - 2.4 vs 3.0 and 11 vs 13. If anyone with experience can tell me ahead of time if that is close enough, it may save me some wasted effort. But I plan to give it a try in the near future.

That is close enough to work. Hook up the K7000 to it, make your adjustments and be done with it :)
 
This is kind of what I was expecting/hoping to hear and it got me thinking, with the chassis from 8liners, it is common to add a resister in line to match the yoke to the acceptable range for the chassis. I wonder if you could do the same thing with a WG or G07 chassis if you can't find a tube that is close enough.
Jayme
P.S. Shanman, I can't wait until Saturday night.
 
This is kind of what I was expecting/hoping to hear and it got me thinking, with the chassis from 8liners, it is common to add a resister in line to match the yoke to the acceptable range for the chassis. I wonder if you could do the same thing with a WG or G07 chassis if you can't find a tube that is close enough.
Jayme
P.S. Shanman, I can't wait until Saturday night.

I'm pretty sure you can't do that. It's not that the signal has to be resisted, it's how it's resisted through the windings of the yoke.
 
I figured I wouldnt be that easy, but since they do it on those new Chinese chassis it got me wondering.
Jayme
 
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