Going back and rereading your original post, I have some questions as to your original plan to digitize your 8mm tapes. I apologize if you already understand the following, but it's unclear from your post since you reference both the desire for an s-video port and the benefits of the firewire port.
It sounds like you originally planned to use the firewire output to input directly to a PC. This would digitize (capture) them, both video and audio, in the TRV-120 in the DV format prior to sending it to the PC via firewire. This is definitely possible and might be adequate for your purposes... and that's your decision, no-one else's
. However, because of the methods of compression DV uses, capturing analog as DV is generally not recommended by those looking for the best quality output.
The recommendations made on this forum to use a D8 camcorder to digitize Video8 (std 8mm) and Hi8 do not involve using the firewire port. Rather, the video/audio is output via the s-video and analog audio outputs to some separate analog to digital capture device/system. Compared to a Video8 (or most Hi8 camcorders), the D8 camcorder gives you s-video (vs composite) and also the line TBC and the (maybe useful) DNR function.
Do you already have another capture device that you plan to use with an s-video output of either the TRV-120 or some other player device? Are you using this already to capture the tapes that do play on the TRV-120? This is unclear so far.
I'm going to be crucified for the following, but I'm going to say it anyway. I would certainly try it myself before assuming it wouldn't work well enough for my personal needs.
so here goes...
Assuming you are already using the firewire output of the TRV-120 to transfer any tapes that do play on it to a PC, have been satisfied with the quality of these transfers? If so, have you tried using the "AV/DV out" function of the TRV-120 to "capture" the composite video output of the Samsung and output it as DV to your PC? Basically this uses the TRV-120 as a "capture device" only. It doesn't have to play the tapes at all.
This method would/will be justifiably frowned upon by the pros and advanced hobbyists who inhabit this site, but it is an option you appear to have with the equipment you have. To get better results, you will likely have to acquire more equipment: a player that will play your Samsung tapes and give you an s-video output and hopefully have a line TBC (like the TRV-120 that doesn't work for you), possibly/probably a frame TBC, a good analog to digital capture device/system. But maybe you already have some of them. It's not clear...
BW
Edit: PS: Just a FYI. When you make a new recording on the TRV-120 it records as DV, not as analog. I believe this is true of all D8 camcorders.
PPS: flame away guys!