If you know what decoders there are in there (maybe after opening the locos up), then getting online to find the documentation for them shouldn't be too much of an issue. Whether JMRI can *find* the decoder in its list of known ones is then irrelevant as you can use the single CV programmer (unless you stumble across a type that's virtually impossible to program unaided, the ones with thousands of (indexed) CVs are a pain).
But when you say that a Power Cab cannot find the decoder, I do get confused. A Power Cab has no knowledge of decoder types and won't look for it; you'd have to do that by hand. So that sort of leads me to thinking that when you say they can't *find*? the decoder, you're actually having trouble *reading* the decoder. And if that's so, then maybe you're not using the programming track? You need to use that in order to read any CV. Writing them CAN be done blind (Programming on the Main or POM) but with two decoders on address 3 on the layout, both will get programmed at the same time. So tkae one loco, put it on the program track, and try again - if that was your issue.
Good luck! If this doesn't work, give us more precise information on what you are doing.
I bought two diesel locos from estate sale: Athearn and Broadway.? Both run great at address 03, but neither JMRI nor Power Cab can find the decoder.? So I can't even reprogram the addresses.? I have ~ 12 locos that work fine so it's not user error, wiring, etc.? How do you find an unidentified decoder?? Power Cab, Power Pro, JMRI downloaded May 2019, Lenovo laptop with Windows 10.
