First of all, use lateral thinking, later it will lead you to
omnidirectional thinking. Change the chips on ONE board and run it
through all the sets, one at a time. Make sure to check everything that
even looks fusible, and of course see it work in at least one set. Once
it works transfer the board from set to set. All the ones it works in,
order chips for them, and get one extra set for a board you keep, to
fix the rest.

You don't even have to screw the board in, just plug them in. The ones
that don't work, go farther, but at least (hopefully) get the bulk of
it out of there. ( or fixed, whatever ).

You need to get to know what the picture looks like without convergence
correction, this way you can make (in the future) an educated guess as
to what's wrong.

Once you got X amount of them fixed, go on to the rest.

Yes, I'm a pro, but I still work for an old horse trader. When you lack
detailed service info, multiple identical units are the best thing to
have.

JURB