Is there a designation printed beside it? Like "RA##"?
The schematics show quite a number of resistor arrays/networks, and I don't have a TMNT PCB to look at...
EDIT: based on a PCB pic i found online, I think you're talking about the R-2R network discussed in this thread a couple years ago:
Coincidentailly, I'm looking for a R-2R network for an Atari PCB, but I need it to be 1K/2K (for the value of R & 2R) vice 100K/200K for that Konami part. Let me know if you find a source with an available range of 8-bit, 10-pin R2R networks...