Thanks FAST6191 & Jorpho for your quick replies.
FAST6191 ~ Intel Hex is a standard data record format in ASCII (so human readable) for defining the contents of EPROM/ROM, etc. The format looks like this:
and continues on with each line indicating the number of Hex Bytes, starting address, and a checksum as the last byte on the line. You can read all about it here: https://en.wikipedia.org/wiki/Intel_HEX
Intel Hex (and .bin) are the only formats I'm familiar with when it comes to programming individual EPROMS, thus I thought it might be a solved problem to extract the .hex / .bin files from the MAME ROM files.
I'll study the .cpp files and (at first glance) these seem to be the C source code for a series of Williams games (Defender among them). I see the memory maps, which may help me figure out the ROM partitions (starting addresses) when considered in conjunction with the electrical schematics which also reveal the memory maps (base addresses for each accessible part of the entire addressable range).
Jorpho ~ I received my ROM board today and it is missing several ROMs, so I'm a bit stuck and can't do the comparison to known good dumps. This is a bit of a chicken-and-egg problem, i.e., how to get the known good dumps in the first place? If I had them, I could burn new ROMs directly. But, I agree it would be good to read the ROMs I have and make a record of them. I could then eventually compare them to other image sources I may come across. Finally, I think you're right about the DOA boards - the ROMs may not be the first thing that fails unless some DC voltages were ever hooked up incorrectly. Chips don't like that and they won't last long under overvoltage or reverse voltage conditions.
I'm hoping a few other members will chime in with links on the ROM .hex or .bin images (or how to convert them from the given defender.zip file, which holds these 15 files: decoder.2, decoder.3, defend.1 ~ defend.12, and defend.snd).
Thanks again for your quick replies and help!