Need code for SV2000 tv/dvd combo & Comcast remote,

If you have already tried all the recommended codes and the "no code option" on your Comcast digital adapter remote, but are still unable to program it to control the power and volume of your RCA LED TV/DVD combo, you may need to consider using a universal remote or contacting Comcast or RCA customer support for further assistance. It's also possible that your specific TV model may not be compatible with the Comcast remote.

If you wish to get more details; check the sites linked here. It has set-up code list & set-up procedure to many popular brand remote controls. Common set-up codes to check with TVs and other devices are given, in the order of the "device's brand name list" in alphabetical order. Pull up older posts.
http://electronicshelponline.blogspot.com/
http://electro-medical.blogspot.com/
http://remotesearch.blogspot.com/
http://electrohelponline.blogspot.com/

There is no setup codes for GPX with Comcast DTA remote control.

I have a sv2000 with dvd need a code

If you already tried the tv codes for your make of tv, the manufacturer suggests using the dvd codes for your same tv make sometimes they use the dvd codes to activate or control the tv on some of those tv/dvd combos. If all this fails you can always use the code search procedure described in your remote's manual, but you need to be patient because this procedure will scan thru all the programmed codes(vcr,dvd,sat,cabl etc.) one at the time.

Any remote supporting Sylvania TV/DVD combos will work for these tvs. I had a Zenith universal remote working with this TV.

The manufacturer for this television is Sylvania, the standard codes for TV/DVD combos will work just fine.

the code for the SV2000 using a oneforall remote is 0456

This is interesting. I have the same TV/DVD combo, lost the original remote and have Verizon FiOS. I cannot get ANY code to work the TV on the universal FiOS remote, not even the Magnavox codes suggested by Phillips, the remote manufacturer.