Hm. I've used this method with a few old Atari computers. I used a known good replacement DRAM chip and carefully placed it over the old chip, making sure all of the legs contacted properly. If there is only one bad RAM chip on the board, you can find it by hopping the good chip over all of the others one by one until it passes testing. Alternately, you can get a full replacement set and remove them one by one until you find the problem chip(s).

If you've got the time, iron and a sucker, I'd just order a whole new set of chips and do them all at once.

Apple II Csa2 FAQ[/url]"]018- What chip can I use to replace a bad RAM IC on my IIemotherboard?

The 4164 (64k x 1) works on motherboards using eight memory chips. The RAM on my motherboard is in sockets; so, it was easy to replaced a bad memory chip with one.

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Jameco sells these for a buck a piece.