[Alastair E]

Converging a delta-gun set--is sorta an art in itself. There's usually a sequence to follow and the setting-controls are usually numbered--but not always.

Sometimes--with the issues you have, the inability to converge the bottom, (applies to any section of screen where it seems impossible to set) sometimes its needed to mis-converge both top and bottom equally while looking at the middle to get that equally out too--Then reset the Statics to bring it all in together, a slight tweak to top/bottom then to get it perfect--However, you'll find that Other parts, say horizontals will then be out so will need re-touching ...

Even though you've set the statics first off--they often need a little tweak in order to get everything lined up, as the dynamics are altered during set-up.

Your vertical Linearity could also be affecting the convergence--That really needs to be sorted before you converge the set in earnest....

Get the picture as perfect as you can geometry wise, horiz. lin/vert. lin, pincusion, etc and in black/white before worrying about convergence then finally color...

I hope you have a cross-hatch generator to work with--Trying to work with a moving picture is nearly impossible!--Simple, maybe computer-generated image or test DVD with various patterns will be OK....

The convergence coils rely on mixing both vertical and horizontal wave-forms to modulate the position according to the scan point on screen. IF the linearity is wrong--so will be the convergence drive signals to the coils....