Save yourself the headache and just get a $50 piggyback board.
I've rebuilt the hv section of those boards numerous times, and it's always a cluster because someone before me had attempted a spotty rebuild seemingly on every single one I've done. Besides, the williams design is undersized for the amount of current being run through that section, and it's only a matter of time before you'll have to do it again. The piggyback boards have substantially larger components, and are of a better design to dissipate the heat that cooks the originals in the first place from running plasma displays.
I'm sure others will just say spring for the colordmd, since it doesn't need high voltage, but you have other options.
Good luck!