What you set (any) TV to will depend on how the DVD recorder is connected and set. Ie: I think you mean it is using a composite cable, so that’s what you would select on the TV. On the other hand if you mean a cable TV-style f-connector connection, then the DVD recorder will be modulating the signal on to “some” channel and you have to tune the same channel in the TV. 3 and 4 are common in that scenario but I’ve seen oddball channels too. The channel may be selected by a switch on the back of the recorder, or somewhere within its UI, or it may be a matter of looking in the manual.
BTW the fact that it won't record, may indicate that the DVD recorder (rather than the TV) is set to the wrong input for how the cable box is connected. (ie: maybe it won't record because there is nothing to record.)
Banned but back. Because why not?