Core problems

I've been bringing my Nicolet 1080 back on line, gradually. I'd written a simple RAM test. No address uniqueness, just a simple read read complement write read complement write sequence. I found a dead stretch of memory on one of my 3 core banks. I figured it might be an address driver or a broken wire in the core. I checked my documents and wouldn't you know it, the wire list didn't include that part of the cores. Only up to the driver board inputs ( typical wire wrap back plane ). I still need to determine if it is a core or driver problem. I can swap things around to determine that though. I was looking at the schematics and found that the drivers were SN75324N. I'd checked on ebay and sure enough, they had them. With shipping they're little over $4 each, for 4, but available ( note that the plastic and ceramic packages have different pinouts ). I suspect the core but that is a project for today. Just getting the machine back to taking instructions and running code is fun. Dwight