HDTV and Cable Troubles, At a Loss of What the Issue Is - AVS Forum
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post #1 of 12 Old 07-23-2011, 12:17 PM - Thread Starter
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I've been having a lot of trouble with my cable and I can't determine where the problem is (my tv, or the cable company). I apologize if this gets long winded but I wanted to make sure I get all of the details.

I currently have limited basic cable with Comcast. I made the change to limited basic earlier in the year. It was working out well for me because I was receiving local HD through my DTV port on my Vizio VX37L. A few month ago a ran into an issue where those stations stopped coming in. When I would tune to one of them, I would get a blue screen and it said "No Audio or Video". I would do a channel re-scan and still had the same results.

Around this same time, Comcast in my area went all digital. Suddenly I was also having lots of trouble completing a scan on my TV. It will almost never complete a scan, always getting stuck on 37%. I did some research on this issue and found some results. However, all of the solutions haven't really helped (I even called vizio and they ran me through the same solutions, which oddly enough worked that time, but failed to work consistently since). So anyway, if the stars align and I am able to complete the scan, the stations are still blue with the no audio or video message.

There are, however, some stations that do come in- about two QVC ones, and TBS. This partly has me believe it is not an issue with the TV, like a busted tuner, because I am getting at less one or two stations. But then I wonder why I am having some much trouble completing the scans. It has gotten nearly impossible to complete them (today I was able to after weeks of trying at least a few times every few days).

I have also tried contacting Comcast on this many times and they really don't know what I am talking about. I did some research online and it seemed like an issue could be with Comcast moving the clear qam channels around as someone said:

Quote:


Comcast may have relocated the channels to frequencies which are blocked by a previously installed filter. You may find the new frequencies by checking at this site -- the filters were installed to prevent theft of services when the channels were analog, so Comcast may be willing to remove them now.

I tried to explain this a few times to Comcast and they said they would pass it along to the engineers but I never heard anything and it obviously still isn't working.

The third wrinkle in all of this that I feel is worth mentioning is that with the digital transition, Comcast states that if you have an HDTV with a digital tuner, you will not need to have a DTA adapter on that TV. However, this does not seem to be the case as if I tried to just go straight from wall to tv, I get the message on the screen saying that if I see this I need to get a DTA.

So this is where I am stuck. If the issue is with my TV, then I don't want to fight with Comcast on this issue. I have been resistant to them sending someone out here because of the scanning issue. If the tech comes and we try to do a channel scan and it gets stuck, then he is going to say it is the TV's problem and they will charge me for coming out.

But could it be that my TV is getting stuck on the scan because of the Comcast system? If they really changed things around with the digital transition and the clear qam, then could my TV just be having trouble processing the channels?

Again, I really apologize that was so long, but I felt it was best to explain as much as I could. Unfortunately I don't have another HDTV here to see if it works to help determine if it is my TV or not. I really appreciate any help anyone can give.
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post #2 of 12 Old 07-23-2011, 07:39 PM
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Quote:
Originally Posted by harrydetroit View Post

If they really changed things around with the digital transition and the clear qam, then could my TV just be having trouble processing the channels?

Bing!

The problem is not all QAM tuners are not created equal. Some have problems picking up all the possible QAM locations.

Keep in mind that after the Comcast digital change over very few QAM channels are available; local HD & SD, public service/gov/edu, shopping, and perhaps one or two others like you've seen with TBS.

If you're lucky you'll find all the local HD stations still there, but just on different channel numbers. Try manually deleting all channels in memory, resetting the set back to factory settings, do a new channel scan, and look at every channel scanned into memory, even those in the numbers over 100.

In Detroit, Comcast puts local HD on the same channel numbers as an ATSC over-the-air tuner would show; for example WJBK FOX is seen as 2.1. If the Vizio is having issues, it may find the same channel on any number over 100. The SD versions of the local channels are usually found between 200 and 210.

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post #3 of 12 Old 07-23-2011, 09:24 PM
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Quote:
Originally Posted by Ken H View Post

The SD versions of the local channels are usually found between 200 and 210.

The SD versions of the local channels are remapped to 2xx with xx being their OTA number.
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post #4 of 12 Old 07-24-2011, 04:59 AM
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To rule out the TV, try attaching an OTA antenna. If you are within close range of the towers, and do a scan, you should pick up local channels with no problem.
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post #5 of 12 Old 07-24-2011, 07:39 AM
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Quote:
Originally Posted by mikepier View Post

To rule out the TV, try attaching an OTA antenna. If you are within close range of the towers, and do a scan, you should pick up local channels with no problem.

+1 .... but remember to scan for the OTA channels when you do, not the Cable channels.

In my basement office, with an old Vizio 22" 720P set I can get 2 ATSC OTA channels with an 18" piece of wire in the jack. If I hook it to a real indoor antenna, that jumps to 5. When I hooked it to an outdoor antenna, there were 15 or more (counting subchannels)

MY Vizio automatically replaces the previous scan with the new ... there is no "add" or anything like that. It was a pain when I had a rotator and couldn't get all at any one rotation angle. I believe newer units have corrected that "error".
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post #6 of 12 Old 07-24-2011, 08:12 AM - Thread Starter
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Thanks for the responses, everyone.

This morning I have connected it to an antenna, and I do get some channels in. So perhaps it is not the tv?

Ken, I have tried finding a way to reset everything to factory settings. There doesn't appear to be an easy way to do this on the this TV. There is a menu option to reset setting, but it seems like a quick reset, not really like a factory reset.

I was able to get it to complete a scan again this morning but I am still getting the blue "no audio or video" when I tune to the channels. I tried going through each channel as you suggested, but most were blue like I said, but I did have some come in. Again, I had TBS in HD, and I had a few other SD channels (one ABC, tv guide, the weather channel, and I think some CSPANs.)

I'm going to keep searching the net to see if I can find anything about more of a hard "factory reset".

Oh, I also wanted to mention that this TV does not have a way to manually add or remove channels. It is all auto scan it appears. There is one setting where I can "skip" channels, but I believe this is more like skipping it when I am flipping through the stations, and not removing it entirely.

I'm still open to any suggestions. I'm not saying I would go this road, but just weighing my options- is there like an external tuner that I can buy that may work better then the one in the tv? Since I am switched to limited basic I have realized that I don't miss the extra channels, so I foresee sticking with this set up for a while. So I don't mind purchasing something if it would end up getting all the HD channels I was looking for. I understand that I will likely only get the Local HD and PBS, etc but that is all I am looking for.

Actually, that raises one last question. If I did get some sort of external tuner, would it still have the same problems as my TV? Or does the TV maybe have a subpar tuner that just can't handle whatever my cable system has changed?
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post #7 of 12 Old 07-24-2011, 09:01 AM
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Quote:
Originally Posted by harrydetroit View Post

So I don't mind purchasing something if it would end up getting all the HD channels I was looking for. I understand that I will likely only get the Local HD and PBS, etc but that is all I am looking for.

If thats all you want, then just use the internal tuner in your tv to pick up stations OTA. You will get the locals in HD plus PBS, plus any subchannels.
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post #8 of 12 Old 07-24-2011, 09:17 AM
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Quote:
Originally Posted by mikepier View Post

To rule out the TV, try attaching an OTA antenna. If you are within close range of the towers, and do a scan, you should pick up local channels with no problem.

It's quite possible the ATSC tuner works fine and the QAM tuner doesn't.

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post #9 of 12 Old 07-24-2011, 09:17 AM - Thread Starter
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Quote:
Originally Posted by mikepier View Post

If thats all you want, then just use the internal tuner in your tv to pick up stations OTA. You will get the locals in HD plus PBS, plus any subchannels.

Thanks for the reply. The trouble is that I don't get nearly as many channels with the antenna then I was getting with the clear qam. Plus, that would be a whole different road to go down - probably having to purchase a better antenna, maybe having to mount it in the attic, having then then run wire through the walls from the attic to the TV, etc. Playing with the antenna I'd have to put it on one side of the room to get CBS, another to get FOX, etc.

When the clear qam was working it was great- locals in HD, TBS, like 5 different PBS stations, etc. and all I had to do was plug in the cable from the wall like I normally do. So getting the clear qam up and running again is really the idea situation.
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post #10 of 12 Old 07-24-2011, 09:45 AM
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Quote:
Originally Posted by harrydetroit View Post

This morning I have connected it to an antenna, and I do get some channels in. So perhaps it is not the tv?

Maybe, maybe not. It's quite possible the ATSC tuner works fine and the QAM tuner doesn't.

Quote:


....is there like an external tuner that I can buy that may work better then the one in the tv?

Yes, you can buy an external tuner for QAM and ATSC. There is a list at the top of this forum. http://www.avsforum.com/avs-vb/showthread.php?t=179095

Quote:


Actually, that raises one last question. If I did get some sort of external tuner, would it still have the same problems as my TV? Or does the TV maybe have a subpar tuner that just can't handle whatever my cable system has changed?

If another QAM tuner has similar results, it would most likely mean the issue is that Comcast somehow disabled the local HD stations for clear QAM reception. This has happened before and is a mistake they will fix, if that's the problem.

As noted, another way to solve the problem is to use an antenna and get the local stations over-the-air. Depending on where you live, different antenna options would need to be considered. In general a directional antenna mounted outdoors as high as possible is the best solution. There are advantages to this approach, including you'll be getting the stations directly from the source (best possible HD image quality) and after you pay for the antenna set up the cost is free. To see what is possible for OTA in your area, go to TV Fool and punch in your info.

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post #11 of 12 Old 07-24-2011, 11:46 AM - Thread Starter
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Well I think I have found the problem, and much thanks to all who made suggestions.

One thing I didn't mention (because I had given up on it) was that I do have an old usb digital tv tuner that I've never really gotten to run with Windows 7. They didn't make drivers for it, and I have tried unsuccessfully to get it working with my main desktop. However, I did remember today that a year or two ago I was actually able to somehow get it to work a bit on a netbook I have. So I pulled that out and gave it a shot.

Sure enough I was able to pull in the clear qam channels! So it does look like the trouble is with my Vizio tv.

Now I have to decide what to do. I could pick up one of the external tuners that Ken linked to, or maybe I could try getting this tuner or a new one to work with a HTPC type set up. I've been using the above mentioned old netbook as one for a few months now, for basically everything but live tv. If I try to use this tuner or a new one, I may be able to make a nice little set up (if the netbook can handle it).

The only thing I have noticed is that the quality is definitely not as good. The HD looks better then SD, but definitely a bit cloudy/muddy. Could this be because of the tuner or would this be an issue with the netbook (which is connect to the rbg on the tv).

Thanks again for the help!
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post #12 of 12 Old 07-03-2012, 01:37 PM
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Vizio has some known problems with their QAM tuners. This "should" do a hard reset on the tuner:

===========================
Vizio suggested another technique that apparently does a hard reset on the tuner. This procedure involved unhooking the coax from the antenna/cable input, unplugging the TV set, holding the power button down for 30 seconds while reconnecting power and coax, then doing a re-scan.
===========================

I found this somewhere on this site but I can't remember where. A friend of mine is having issues with his Vizio QAM tuner also.
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