Intermittent Reception Problems on Vizio HDTV on Cox Network (Updated with partial solution) - AVS Forum
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post #1 of 10 Old 08-20-2012, 05:22 AM - Thread Starter
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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.

Questions:

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.
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post #2 of 10 Old 08-20-2012, 10:03 AM
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Does the television simply search for information transmitted by the cable provider and store that information for later use?

Correct, and if the cable company ever changes that, you will not receive that channel until you re-scan.
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Are the channel numbers to be used by a QAM tuner determined by the cable provider, not the television?

The cable company. This is why every tv you would have, regardless of make or model, can tune to the same channel, i.e. 128-3 on qam would be the same channel on any tv connected to the same cable company.
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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?

No, a tuner is a tuner. The cable company has no way of sending different channels to different tv's. (well, except for cable boxes, which doesn't matter in your case)
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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?

Do you have access to another, non-vizio, tv you can test? Honestly, I have a hard time believing that the new tuner and the new tv they sent you would have the same problem tuning the same stations. But, since your smaller tv has absolutely no problem tuning these channels regardless of location in your house, that by itself proves the cable signal coming into the house is fine. But, when you say the problem is happening basically every hour, there is always a possibility that the cable company is sending something else along with the signal. I have no clue what it would be, but that's just odd.

So I would suggest if you can find a friend or neighbor with a non-vizio tv, try that and see what happens. If not, you will just have to keep going back and forth with Cox and Vizio until one of them figures out the problem. Perhaps Vizio could send you out a different model.
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post #3 of 10 Old 08-20-2012, 11:52 AM - Thread Starter
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Thanks Sitlet,

Everything you say makes perfect sense to me, which is why I don't understand what is actually happening. It makes no sense that my small 22" TV can continue to display a WETA program on channel 26-1, but the 55" TV uses channel 40-5 to display that same program. And I don't understand why the 55" television was able to find channel 26-1 the first time the setup program was run just a few days ago, but on any subsequent channel scans the WETA station is assigned to channel 40-5.

As far as loss of signal is concerned on the 55" TV, the problem doesn't necessarilly happen every hour. It may skip an hour. But when the signal loss does occur, it is usually precisely on the hour. Also, why isn't the 22" TV affected?

Again, thanks for the input. Other than the two Vizio televisions, the only other TVs I have are old none HD units that have CRTs which will be of little use. Perhaps I can find someone in the neighborhood who can lend me one.

Like I said, you make perfect sense to me. I just wish the facts on the ground here made sense.

Again thanks for the input.
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post #4 of 10 Old 08-27-2012, 08:03 AM - Thread Starter
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Since my original post, I have found a solution to the stations in question not being displayed on the same channels as they were after the original installation of the television. I found this information on the Vizio website. It seems that when the television is set back to original factory settings, that may not actually happen so it's necessary to run a channel scan with the cable connection removed, then connect the cable line again and run a new scan.

After following the procedure below, I now have the WETA stations on channels 26-1 through 26-4 and the other stations on channels 50-1 through 50-3.

I am still having problems with losing reception of the video or video and audio. A third Cox technician has been in, but without any positive results. As I collect additional data however, it does seem that the loss of signal is most likely to happen exactly on the hour. The signal may be present for a couple of hours, then vanish. So, I suspect that something being transmitted is causing the problem.

Below is a quote from the Vizio website.

Follow the steps in this order:

• Power off TV
• Unplug TV from outlet
• Press and hold in the power button on the TV for 30 seconds (while it is unplugged from the wall)
• Release the power button
• Plug in the TV into a different outlet
• Power the TV back on

There is also a factory reset option in your menu under the SETUP section. It will say either "reset all settings" or "system reset".

Once the above steps are complete please remove the cable connection from the DTV/TV connector on the back of your television and run a channel scan to clear out the existing channels. How do I do a channel scan?

Once this is complete plug the cable line back in to the DTV/TV connector and run a new channel scan.
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post #5 of 10 Old 08-27-2012, 03:30 PM
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Not that this is going to help you any but Vizio has a long history of qc issues with their sets. Some are fine but if you go thru the various threads here you'll see that a large percentage of issues are Vizio related. Quite often they would rather replace your set than fix it because they can't, or won't, fix it. Quality parts are an issue at times. If you have one Vizio set that works all of the time then it's not Cox. It really does sound like whatever tuner they are using for your set it can't properly scan, and then remember the stations. My guess is that your 22" has much better tuner than the 55".
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post #6 of 10 Old 08-28-2012, 10:39 AM
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You can go to TVFOOL.com and find out the stations "digital name" their old channel number and the actual RF channel number they are now trnamsitting on.
For example old Channel 35 may now be namned "35-1 and actualy be broadcast or RF channel 73.
Digital signals will fail to be processed at all if their signal is too weak or if they areB] too strong[/B]. your small TV may have a porer quality tuner then you new large TV and not reject stonger signal.
How far are you from the antenna towers?
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post #7 of 10 Old 08-29-2012, 08:41 AM
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Originally Posted by walford View Post

For example old Channel 35 may now be named "35-1 and actually be broadcast on RF channel 73.
While I agree with your general info ... I kinda doubt anyone is actually broadcasting on RF channel 73 ... in the last "few" years.
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post #8 of 10 Old 08-29-2012, 11:53 AM
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LOL.... "few"?
I guess to some, ~30 years may be a few. biggrin.gif
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post #9 of 10 Old 01-06-2013, 02:07 PM
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Here is something I noticed after have the same type of problem with my 37 inch Visio tv but I only noticed it on channel 2-1 which is the HD cox cable channel in my area. Channel 2, the analog channel always works fine.

I have a power chair recliner plugged into the same wall socked as my tv. Every time I recline, the tv looses its pictuer then returns after the reclining motor stops. I also have an electronic vibrating machine that when I turn it on, the tv looses its signal....note that it is plugged into the room electrical but a different outlet. It is located about 5 ft from the tv. I uplugged the electrical vibrating machine and with an extension chord, I plugged it into another room. I then turned it on again and the picture was distorted, but no complete signal loss.

You migh check the room for some type of electrical interference.
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post #10 of 10 Old 01-06-2013, 03:41 PM
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^^^^ at one time I had the same room setup that you have. TV and electric reclining chair on the same electrical circuit. The tv is an LG and never had any problems at all with interference. It's poor circuit protection design on the Vizio.
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