This expert is helping you out because there weren't many active Comcast experts.
first, press cable up at the top of the remote and then press power.pay attention to the lights. unplug the power from the back of the box briefly and plug it back in . both lights should flash and i think the amber one will stay lit. if you wait about 2 minutes you can try and turn it on with the remote and the green light will come on. hopefully you have more than one remote in the house so you can rule out a remote problem
theres a slim chance its downloading firmware so just leave it plugged in and try all this again in an hour.
The Cable Guy
I fix it everytime
First check the power cord and try pressing the power button on the box itself. If this doesnt work or there is no power button try swapping the batteries in your remote and trying to turn it on again. If both the above fail take yor box to your local service center and swap it over the counter. If you have no time to go to a service center you can schedule an appointment for a tech to come out which should be free since it is most likely Comcast equipment causing the issue.
DCH70 boxes are notorious for power supply burning out. If you unplug and plug back the box from electricity and have no power light at least flicker on the box then your power supply or even the box itself are bad and need to be exchanged. At that point trip to payment center or tech appointment will be necessary.
11 years experience offering one post resolution
People return these boxes all the time it is possible that you were given the wrong power cord for the box and it burned out. Some of the Motorola modems have a very similar power cord that will fit the box but it will also burn out the box. If they have the older style boxes you would be better off taking one of them although much larger they are more reliable. Please make sure to bring the box and powercord with you.
Commercial service and installation technician, been with the company 8 years doing technical troubleshooting...
Upgrade to a newer box, call for a tech to come and swap it or go to your local office and swap it there.