I have a Comcast cable box connected to my Panasonic TV via HDMI cable. When I use the ALL ON button on the Comcast remote, it sequentially turns on my equipment, cable box first, then TV. Recently, the TV comes on with picture, but no sound (up until last week, it had been working perfectly).
When this happens, if I cycle TV power off and back on (without turning the cable box off), the sound returns. Or, if I manually turn the TV on first, and then turn on the cable box, there's no problem.
I have isolated the issue to the TV by doing the following:
Got a new cable box, remote, and HDMI cable from Comcast. Still same problem.
Then I connected to new equipment from Comcast to my other TV (a Sony). No problems.
Panasonic won't offer any help because the TV is out of warranty.
This kind of problem with HDMI is pretty common. I would just leave the cable box on. If it is a DVR it is pretty much on 24/7 anyway. If it is a regular box the difference between standby and on should not be more than a few watts.
americanaudiophile, your reply is pragmatic, but I already know how to work AROUND the problem. What I want to know is how to FIX the problem. I know it's a real problem because until a week or so ago, everything had been working properly for about 18 months. I think I've isolated the problem to the TV (see my complete post for the troubleshooting steps I've taken). If this kind of problem is pretty common, as you state in your reply, then somebody should have a technical understanding of what's happening. I can't believe that a glitch this common would not have been addressed. Otherwise, the HDMI interface is not really ready for prime time.