If you just split the signal to the DVD R without any kind of box, then you will limited in the number of channels you can receive (and that could be none if your dvd-r is analog only) That is why I suggested the DTA, it can be used as a dedicated tuner box for the dvd-r. You would still keep your other box for the TV. In most areas a couple of DTAs are free so there would be no cost to get at least some of the functionality back for your DVD-R.
Now the above assumes you are still interested in SD. If you want to move up to HD recording there really are no inexpensive solutions.
As stated, the dvd recorder can only record what the comcast box provides to it. You can get a DTA (a small decoder box) from comcast that will output the SD channels in analog (up through the digital starter package lineup.) Generally up to two of the DTAs are free per account (can vary by local area.) You can split the line and hook the DVD R up to the DTA to allow recording of a channel you are not watching. You do have to pre-set the DTA to the channel you wish to record, just like a regular box.
OK. A few things. If you have a normal cable box now not the free dta your recorder is not going to work the way it use to. From the invention of the vcr some thirty years ago if you have a cable box you have to leave the vcr dvd recorder on channel 3 and you can only tape what your watching.
In your case its the same you cannot use the dvd recorder to scan for channels what is it going to scan? it cant scan the cable box. You have to go from the cable in to the box, box out to the recorder in and then out to the tv, you need to leave the recorder on channel 3 and only change channels with the box, you can't use your recorder to record various channels if you have a box.
The tech who brought you the box should have told you this in my opinion. This is why everyone has a rented dvr now. Sorry to be the bearer of bad news.
I received information from Comcast that I would need a box in order to continue to get anything above channel 25. After the box was installed by the tech, my DVD recorder would not record from the TV.(I have an HD TV.) Here's my experience, blow by blow.
1. I checked the connections: wall to box, to DVD player/recorder, to TV. All seemed right.
2. I performed a new channel set-up on my DVD player/recorder. It found the new channels.
3. When I went to program a new recording, using the DVD player/recorder remote, it would only find the channels if the Xfinity remote was used to select the channel.
4. I set the channel to the one I wanted to record, went back into TV mode (using the TV remote) and tried to watch a different channel while the DVD player/recorder was recording what I had programmed.
5. When I played back the recording, it had only recorded whatever I had been watching on the TV. It started out with the channel I had originally selected, and then switched when I changed the channel using the Xfinity remote.
How can I fix this set-up so that I can pre-program my DVD player/recorder to record one program while I watch a different one?