Need help hooking up Hotronic ap41 TBC
 

I am trying to hookup a Hotronic ap41 TBC to my Samsung DVD-V6700 DVD/VCR Combo. I used a BNC-to-RCA adapter to connect the TBC's BNC Video output to the VCR's Line 2 Video Input, but I don't see any difference in the video playback of the tape. Please help.

External timebase correctors are created for the purpose of what I refer to as "cleaning the signal" -- meaning there are little to no visual changes that happen.

Only line TBCs embedded in certain devices (mostly high-end S-VHS VCRs) serve to "clean the image", but provide little to no cleaning of the signal itself. The TBC inside is usually integrated with a DNR (digital noise reduction) circuit or system of circuits.

This is why an optimal workflow includes both a VCR with a TBC, and a separate TBC, so that you can cover both bases.

To digitize a signal, it has to be free of signal noise, which would otherwise cause dropped frames, picture loss or be detected as a false anti-copy. The last one tends to be the errors most common, where home videos are detected as having "copy protection" from oversensitive devices. Analog copy protection is nothing more than an artificial video errors, and there are plenty of actual video errors that can trip up these detections. Analog was a pretty chaotic format. The external TBC takes care of this.

External TBCs, at most, can sometimes reduce jitter, maybe correct for a small [tiny!] amount of color noise.

On a combo deck, you'd have the following setup, if it's allowed by the deck.

VCR > analog output (composite? s-video?)
VCR output > TBC input
TBC output > DVD recorder input
record

I can't do that because the VCR Output is connected to my DVD recorder.

You'll have to create a setup that allows for the signal to pass from VCR to TBC to DVD recorder. That might mean a new VCR, or a new DVD recorder, if the combo won't allow for it. There's no other way for the TBC to work, if it can't pass the signal.