You are not the only one. I made this video some time ago.
https://m.youtube.com/watch?v=j1iN4ULZcX4
If you get a Panasonic box like mine make sure it's got the same letter suffix as my model.
I believe my model ends in "a". The non-"a' versions will only work with panasonic decks, but the "a" supports JVC and probably every brand.... Or at least that is what someone on a D-VHS facebook group I started claims.
Sixteen nine times website while gone was captured by the archive.org wayback machine and its last iterations can be read there.
Sixteen nine time modified several brands of cable, sat, and DTV boxes (I'd really like to find a Zenith since they designed the RF layer of ATSC and had one of the best reciever chipsets of the day). I got a Sixteennine time modified RCA Satellite/DTV with my D-VHS decks... It still works via ATSC (I never had satellite, and ditched cable shortly after that video was made) and my RCA box never needed a PC to record or play back with my decks.
You may be able to look up a manual for your rig on their site through the wayback machine.
I haven't seriously tried to play D-VHS back to or record D-VHS directly from a PC via Firewire before... There are people who have described the software to do it on various OSs, but I haven't had time to confirm advice I have seen, and I have little faith in home PCs to not hickup and ruin a recording.
Not sure I was helpful but, I think I at least gave you some trees to shake for more info.