Convergence ?

[Electronic M]

Originally Posted by Alex KL-1

Some time ago, thinkering and playing with my delta gun TV (a "last generation" delta-gun; the only delta in my small collection), I almost created a thread for the convergence issue, but then I found that the TV certainly dropped, and purity is not consistent also.
This affected one side; the left side converges scary unbelievably good, basically textbook perfect, but right side, the G is not || to the R+B (coincides with bad puruty)... this is strange; normaly I see people complaining about R or B not converging to the others... this G lost even don't make sense to the convergence panel adjustment descriptions.
So, I think I can need to live with it, until I found another set.

Or, is worth to try to play a little with it?

PS.: this tube also have another problem, but I think is about the socket: is very inconsistent with focus. But, I dunno why the image is more dim when focus is wrong, go figure... (well, I never worked with delta gun CRT, so I dunno if it is a normal behaviour, or...)

There are things you can do. First thing I would try is using an external service degaussing coil to try and get the impurity to go away, then if it doesn't I would go through the purity adjustments and see if I could adjust it out. (Edge purity is highly dependent on deflection yoke position so doing a full by the book purity may fix it). If that doesn't fix purity maybe try a refrigerator magnet on the bell near the bad spot as a last ditch.

EDIT: to keep from going off topic others mentioned some sets are a pain to converge... I've found 2 things influence that bad convergence board parts (R,C and diodes), and convergence yoke placement and warping. Sometimes the yoke needs to be back or forward ~1/4" from where it's at to either have more range or overshot less, I've also seen some plastic yokes where one set of petals is angularly closer than it should be due to plastic degradation... That's not easy to deal with.
What probably gave me my worst headaches until I realized was a 19" metal cabinet Zenith a respondent to this thread sold me a while ago...I spent a bunch of time troubleshooting the board because of top hat diodes that looked like they'd been soldered in by Ray Charles, then finally realized that the convergence yoke was installed BACKWARDS and the red yoke petal was over the green gun and vice versa....It got really good when I fixed that.