Hello , my name is Jack Perhaps I can help you with this problem but first i would have a few questions;
Ca you tell me what type of cables/ connection you are using to connect the cable box to the tv ?
Is it HDMI , a coaxial cable connected in the TV's antenna/cable terminal at the back or color coded cables/plugs ?
Do you have the TV's original remote ?
Coax cable connected to antenna A in back of TV. No, cannot find original remote. Using buttons on front panel of TV.
O.k then the A3 that you see should mean antenna A channel 3 which normally should do the trick unless your cable box output is set for channel 4 .
When you tried the cable box on another tv ,was it with a coaxial cable and did you set that tv to channel 3 or 4 ?
At the back of your cable box ,are there audio/video out terminals red/white/yellow ?
On the second set, I just plugged in and channel was already set on ch. 3 Cable box output is also on 3. The cable box is just a small box with cable in, cable out and power.
O.k and you used the same coaxial cable to try it on the other tv ?
If you take the cable from the wall outlet and plug it directly into the tv , do you get anything ?
I'll try that right now. I've never by passed the cable box.
Ok, plugged coax directly from wall to back of TV, antenna A. I still get no picture nor sound. Black screen except for the A3 that comes up in the top left hand corner
O.k then usually although the signals have gone mostly digital hence the box you have now , there should be some analog signal left in the cable system for lower channels like channel 3 .
That small box that you have now , should be a DTA (digital transport adapter) supplied by Comcast perhaps ?
O.k then what I`m thinking at this point is that your TV's tuner went defective and by the way this would have nothing to do with the X-box , just a coincidence.
If you did a channel scan and did try that DTA box on another tv and still not getting anything then the only conclusion is that there is a problem with the TV's tuner.
If you had an old vcr or anything that outputs on channel 3 you could verify that.
Right now it doesn`t mean your tv is unusable , it just means that unless the tuner part gets repaired , you could use an audio video input on your tv.
Either by getting a cable box that do have audio/video outs or better yet HDMI or using another piece of equipment like an old vcr as its tuner .
Do you happen to have an old vcr that is still functional ?
Not for playing tapes but to use its tuner.
I think I have an old VCR in the storage room. I'll dig it out and try to hook it up
O.k then in this case you would connect the DTA box in the vcr`s antenna input and set the vcr to channel 3 .
Then connect a set of audio/video (red/white/yellow) cable out of the vcr and in one of the TV's audio/video input and set your tv to that input .
That should do the trick.
If the vcr mechanism has not work in a while then do not try a tape , it might get stuck and cause the vcr to become non functional even as a tuner.
By the way , you will also have to set the vcr to VCR mode , usually you will have a button on it that will say TV/VCR , just press it .
Also , if the vcr was functioning correctly before you stored it then you could perhaps try a tape to verify the good connection or functionality with the tv
Let me know how it goes
Hope this help and please take the time to rate my answer if that does the trick , otherwise do not rate at all , just let me know and we`ll see what can be done.Note that you can reach me here at any time after rating if you have questions.
This worked. Have picture and sound. Can I replace the tuner myself, and are they expensive. Just in case I get ambitious. I do have some technical knowledge
You can actually get it at the link below;