I have a Philips TV as well and is does power off after following the enter codes procedure. BUT will not power on unless I press another key first and than the power button. I see that your model this would not work. If your TV remote has the setup button to be able to program another device to control you could program the DCT or DTA box to be controlled by your own TV remote, you can also buy a 3rd party remote that has that option for about 10-20 bucks. Try these codes for the DTA codes to pgm into the either your TV remote or 3rd party remote 01376, 00476, 00810, 01187, 01254. Comcast website or representative can give you these. I hope this works for you.
Tired of Comcast problems. I have a remote for a digital adapter that will power off but not on. I have tried ALL the codes for Philips/Magnavox TVs; "enter" before power on/off; CH+ before power on/off. Experienced the ABSOLUTE WORST customer service I ever received from Comcast when my cable was cut in error by a Comcast tech who was checking problems for another address and cut my cable wire instead; I spent two days trying to get my service back on when it should have been top priority. You would have thought I was asking for a special favor by the runaround I got.