I must be doing something simple but wrong, and I can't figure it out. I'm trying to be able to record video/audio from either of two sources.

I can successfully record directly to a new LiteOn 5005 DVD recorder in two ways. One is the "normal" way of playing a VCR (through the 990) and recording it on a DVD via the 990's Video 1 Rec Out S-Video connection. I can also record directly from my Set-top box, which plays to a DVI/HDMI connection, but which records via an "archive to VCR" option with an associated S-Video (and audio) port. But what I'd like to be able to do is record from either without moving the cables from the 990's Video 1 Rec Out jacks to the STB's S-Video/audio jacks.

So what I tried to do is route the S-Video output from the set-top box to Video 1 In on the 990 so that I could have either that or the VCR as the source that puts the signal on the Video 1 Rec Out port. I then ran S-Video/audio cables from the Video 1 Rec Out port to the DVD recorder. The first part works--the STB signal shows up on both the HDMI and the Video 1 In ports (and the VCR shows up on its own port--Video 2), but there is apparently no signal coming from the Video 1 Rec Out port (which is monitored on the DVD recorder).

I suppose there could be a bad cable, but I'm getting neither video nor audio signal at the DVD recorder.

Any suggestions for what I should try?

Could it be that the Video1 record out is inactive with Video1 is the active input? Does the input from the VCR in Video2 make it out through the Video1 record out?

Mike in Virginia has touched on a subject that is dear to my analog heart. For many years, a true tape loop was de rigeur on any respectable pre-amp. My first rencounter with the abandonment of what I consider an absolute neccessity, when digital technology started appearing, occurred when I replaced my Sony ESD2000 with a Sony ESD9000. After writing very critical letters to Sony and Sound & Vision Magazine, I bit the bullet and built a passive switching unit which could accept inputs from any of my sources, and route them do my destination unit(s), which were in turn routed to the pre-amp, providing me with full recording monitor capabilities. I got the 990 when my ESD9000 died (no great loss), and still use my home built unit in a similar fashion.
Gonk is absolutely correct that you disable the Video 1 "out" when you select Video 1 "in", as that is a neccessary requirement to avoid creating a signal feedback loop. There is, however, a workaround with the 990, which I use in addition to my home built unit. Use the zone 2 output to feed your destination unit and select your desired source for zone 2. Then select your destination unit for the 990's main zone. A caution to observe here relates to my above statement about not creating a signal feedback loop. DON'T EVER SELECT THE SAME UNIT FOR BOTH ZONE 2 INPUT AND MAIN ZONE OUTPUT.