What do you mean by the "source code"? The machine language level code on their mP? If that is gone, it is toast. You may be able to relace an EPROM, but not if it is surface mount technology, which it most likely is. I suppose you already contacted Moeller?
If by "source code" you are referring to the user programming, and the unit is still operating, you should be able to extract the program from the PLC into their software package. You will have lost all your notations and references however.
"Venditori de oleum-vipera non vigere excordis populi"
If you want to save it for future use, like most PLCs the notations and most of the cross references are not stored in the PLC memory. At 56kb max., there just isn't enough room. All of that information is typically stored in the programming software package. If you are worried that you (or someone) will lose the software, it is a valid concern. I usually print out a hard copy as a backup, and store a version as a text file (although some don't lend themselved well to that). In one extreme case, I printed the program to an Acrobat .pdf file and saved it "electronically" that way, although that was essentially just an electronic picture of the file, not the real data that could be reloaded into the PLC.
"Venditori de oleum-vipera non vigere excordis populi"
