Wang PC260 memory fault

Hi List, So a good friend of mine recently resurrected his childhood 286 Wang PC260 after I suggested he replace the keyboard controller. In the 14 or so years it's been unused, it has developed a memory fault in one of the conventional memory banks. The memory is soldered to the board so we're looking for anything that might assist in tracking down the dud memory IC. He can get it to boot if the memory size is set to 256kB, so I'm guessing the second 256kB bank is bad. Is there software that exists that can identify individual dead or faulty memory IC's, or at least the corresponding bit(s) which may not be working? According to Dr. Google, this machine was built by Tandy for Wang. Perhaps there's a Tandy diagnostic disk that'll work with it, or better yet a Wang diagnostic disk. (I'm wondering if this question has been asked/answered before too) Cheers, Alexis.