Hmm, well the sound is only working on some channels, so clearly the sound does work on your tv. To be sure, try switching that tv with another tv in your house to see if those channels do in fact get sound on that tv. I'm thinking the problem could ultimately be with your tv service provider rather than the tv itself. For example, if you have cable etc. there might be a problem with the cable box itself and not your tv. Most times those boxes are refurbished. Which can lead to slow service & malfunctions of all kinds etc.

I'm not sure what kind of outlets there are in Brazil, but if they're not what we have here in the United States you may need to invest in a converter so that you can plug in your DVD player.

I'm a little confused on your question. If your DVD is built into your tv then I would say it's one unit. However if you have your tv and then a separate box for the DVD player then you got 2 units. I'm not sure if that was what you were asking, But I hope I've helped in some way.