Hi Tedoo,
Your posts kinda include a couple of questions and possible answers now, so I'll try to separate those:
Is the D8B all digital, or can you send signal back out before it gets A-to-D converted?
If you have analog signals coming into the Line or Mic inputs, you can tap the signal while it's still analog, from the Insert jacks on the first 12 channels.
After the insert point in the D8B's signal flow, it will hit the converter, and from there, everything is digital. (To be honest, though, I think a Signal Flow diagram exists, but I didn't look for it for this answer. The above just seems logical to me).
I assume that tapping the signal at the Insert, isn't really what you're looking for to integrate the Radar System as the multi-track recorder.
How do I connect the Radar System to the D8B like a Multitrack Tape Machine?
This depends on what I/O cards you have installed in the D8B, and what I/O options you have on your Radar system. I just read up on it for a moment, and it seems that both, the Radar I and Radar II have TDIF I/O ports? I didn't quite understand how many, though. IF the Radar has 3 TDIF connectors, and your D8B happens to have 3 DIO-8 cards (ADAT & TDIF connectors), then you could transfer 24 channels between them digitally, and without repeated AtoD, DtoA and AtoD conversions. This would also be how the D8B is supposed to work. The TDIF I/O would then appear in the D8B as Tape Sends and Tape Returns - so, exactly how you'd want it to work with a Tape machine (and kind of like using a Mackie HDR with ADAT or TDIF cards).
I haven't used a RADAR system personally, but heard people rave about the converters back in the day (I never heard anybody rave about the D8Bs). So, if at all possible, I'd set it up to use the Radar's converters and interface digitally with the D8B.
I don't see a signal when I connect a Mic or Line source (with the button in the right position). Why?
The first thing I'd check, is if you're on the right "layer". To the left and a little up from the "Speaker Level" knob, are three buttons labeled "Mic/Line", "Tape In" and "Effects". Make sure "Mic/Line" is pressed, to activate that layer for use on the D8B.
If you are on the correct layer, then you should see levels here. If not, then there's still something wrong. Could be a bad Startup song (delete Startup song, restart) or a hardware issue.
If it's the latter, and deleting the startup song doesn't work, then I'd need more details... what's connected where, exactly. Is the startup song using the default settings, etc. etc.
Anyway... let's check for this stuff first, and take it from there.
Happy Thanksgiving!