I think the first thing you need to check is your mechanical setup. If you search these forums, you will note that the experts all harp on and on about how important mechanical setup is.
From my own personal experience so far, this is the most important advice to date, for minimising convergence drift (and everything else for that matter)!
First, make sure you have the PJ mechanically centered and squared / aligned to the screen at the correct distance / vertical screen offset, then make sure you have your rasters mechanically centered and mechanically skew aligned on the tube face (with all electronic controls centered), then make sure you have your red / blue tube / lense angles mechanically aligned for best physical screen convergence, and finally make sure you have your lens flapping ("scheimpflug") mechanically aligned for correct edge to edge / corner to corner focus (with the lense angles of course still set correctly for best mechanical convergence).
Then, when you have done all that, go back and do it all again, before you consider going anywhere near the electronic convergence!
Convergence drift is mostly a function of the temperature coeficients of the various electronic components, so if for example you are using twice as much electronic adjustment on the red deflection drive circuitry than what you are using on the similar blue deflection drive circuitry, you can expect the temperature drift to vary between the two.
With good mechanical setup and convergence, you should only need the minimal possible variance from center in your electronic adjustments.
One possible way of verifying this on your setup, is to carefully measure the amount and direction of drift in each color between cool and warm operating temperatures. You could then try centering all of you electronic controls (everything will probably be out of convergence when you do this), and then do the same drift measurements. Then compare the results. If you find that you have less drift with all of your controls centered (as would be expected), then this confirms you need to pay more attention to your mechanical setup.
Of course, I might be way off track in your particular case, but never the less, another reminder about mechanical setup is good food for thought especially where convergence drift is concerned!
Greg
