Let me start by saying that I am old enough to remember when all of the kids in the neighborhood would be invited to watch at the single house in the community that had a TV. And as far as technical ability, I'm probably more comfortable pulling vacuum tubes to take them to the local drug store for testing. I'm sure not many people here remember that era.
About a month ago I started having problems with the reception of several channels on one of my televisions. The television is a Vizio XVT473SV HDTV, which is still under warranty. The problem was that the video signal or both the video and audio signal would intermittently disappear from selected channels. These channels include 26-1, 26-2, 26-3, and 26-4 all of which are PBS channels for WETA. The old analog station for WETA was channel 26, which is still present. Additional channels affected were 50-1 (DC-50 CW), 50-2 (Antenna TV), and 50-3 (THIS). Finally, the reception disappeared all together. For about a year prior, all of the channels had been received on this set just fine.
I do not have a set top box for cable.
I have a second 22" Vizio television (model number E221VA) on which the reception for these stations is fine.
Prior to calling technical support, I tried several things to acquire the missing channels. First, I tried a partial channel search in the 26 and 50 channel ranges. Next, I tried switching coaxial cables. The coaxial cable to the room where the TV is located is an old style that contains two separate cables paired together. Only one of these cables is in use. To rule out the possibility that the problem might be cable related, I switched from the cable in use to the spare cable. In addition, I removed all unneeded splitters from the cable run. There were two.
I then called Vizio technical support. The person there had me reset the TV to original factory default settings and initiate a channel search, which we did several times but did not restore the missing channels. Then I moved the 47” television to the location of the 22” television that was receiving the missing channels, and we went through the same process without a positive result.
Vizio technical support determined that the problem might be a defective tuner in the TV since one of my Vizio TVs was receiving the stations and the other was not. They made arrangements to have a new tuner shipped in and installed.
The newly installed tuner did not resolve the problem despite several hours of trying. The 22” TV was connected to the coaxial cable at the 47” TV location to confirm that the channels were being received regardless of where in the house it was connected. Finally, the new tuner was removed and the original tuner reinstalled.
I was asked to call the cable service provider (Cox) to see if any changes had been made recently that would affect the problem stations. They said that no changes had been made.
To their credit, Vizio determined that they would ship in a replacement television, but the only replacement available for my model was a 55” version of the same TV.
When the 55” television arrived, I went through the setup process. Initially, all of the missing channels were there and working fine. However, within a day, I again lost video or video and audio on the affected channels. You could tune to the channel numbers but the video or video and audio would be missing.
Vizio thought it unlikely that the same problem would affect two tuners in the 47” TV and a newly installed 55” TV. I was asked to call Cox for a possible solution.
The first Cox technician replaced a splitter at the service entrance then removed my Radio Shack amplifier/splitter from the system and replaced it with a non-amplified splitter. He then did a channel search on the 55” TV after which none of the affected channels was present. You could no longer tune to the affected channel numbers.
He then removed a “trap” from the Cox network box in my yard, after which we set the television to its original factory setting and went through the setup process. Again, you could no longer tune to the affected numeric channels; however, we did find that the stations involved were on other numeric channels.
Old Channel Number New Channel Number Station
26-1 40-5 WETA HD
26-2 40-6 WETA UK
26-3 40-7 WETA Kids
26-4 40-8 WETA
50-1 40-3 DC-50 CW
50-3 40-4 THIS
50-2 40-809 Antenna
But there was still a problem. Within the day, video and audio intermittently disappeared from the new channels.
A second Cox technician reinstalled the “trap” in the Cox network box in my yard, but was not able to resolve the issue of the video and audio signals disappearing.
Since the second technician was here, I have located both the 22” and 55” television to the same room so that I can observe the behavior of both, connected to the same coaxial outlet, at the same time. The 22” television still receives the affected stations on the 26 series and 50 series numbers. The 55” intermittently receives the affected stations on the 40 series numbers.
I am confused about why one television receives uninterrupted service for the affected stations and the other television has an interruption of either the video or video and audio even though they are connected to the same cable outlet.
If I am correct, the Cox signal is comprised of a video signal, an audio signal, and other data to further identify the signal.
I think this may be important. I have noted when the video disappears on the 55” television; it frequently, and perhaps always disappears precisely on the hour according to the clock in the room where the TV is located. I’ve only made this observation within the past day or so. This leads me to suspect that there may be something in the Cox broadcast that is contributing to the problem.
1. When a setup process is initated on a television, is it true that the television has little to do with the assignment of stations number? Does the television simply search for information transmitted by the cable provider and store that information for later use? Are the channel numbers to be used by a QAM tuner determined by the cable provider, not the television?
2. Would the cable provider transmit video, audio, and other data so that the same stations would be displayed on different channels on multiple televisions? If so, why?
3. Is it likely that my problems are caused by the cable provider’s signal, a defect in the design of the television, or both?
4. Could there have been a change in the data that Cox transmits that would affect the larger but not the smaller TV?
6. What else do I need to know to solve this problem?
Let me apologize for the length of this post. As I’m sure you suspect by now, I’m somewhat confused by all this. Thank you for any clarification you can provide.