HDMI Cable or TV issue? - AVS Forum
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post #1 of 12 Old 05-17-2010, 09:52 AM - Thread Starter
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Hi All.

I need some help with troubleshooting. I just got a 50" panasonic VT25 and I had to also upgrade my Comcast digital cable box to the HD version to take advantage of the HD content (this is my 1st HD TV).

When I initially had the HD cable box hooked up via a 1.4 HDMI cable, intermittently, but fairly frequently, when I changed the channel, the image would flicker and give a high pitched "erp" sound as the channel switched. If the channel change happened slightly slower for whatever reason, there was no problem. Exchanging HD cable boxes and trying different HDMI cables didn't make a difference.

When connecting the HD box using the component-out to the TV, there's no problem. When using the non-HD box connecting via a coax cable, there's no problem.

So it was looking like it might be the new TV that was the problem... but I called Comcast. The rep didn't really think it had anything to do with the cable signal but they reset the cable box remotely (their solution for everything), and it actually made a big difference (though it did not solve the whole problem). Now there's only some flickering of the picture when I change channels, but only when I'm on HD channels and it happens about 20% of the time or so. The annoying sound is gone.

So my question is: could there still be something wrong with my new TV? Should I buy some expensive cables (I've got the cheapest 1.4 HDMI cable I could find at Fry's and the coax is the same old one that Comcast installed in 2004)? Should I have Comcast come out and try to improve the signal? I'm not really fond of the idea of exchanging the TV; it'd be quite a headache and since the problem improved with the reset of the cable box, my suspicion is that it might not be the TV.

Thanks in advance,

- Frank
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post #2 of 12 Old 05-17-2010, 10:54 AM
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Your comcast cable box has an HDMI 1.3 output chip and all you need is an HDMI 1.3 cable. It may be that the 1.4 receiver chip in the VT25 is sending back information that the Comcast box does not understand.
There is very little, if any benefit, from using HDMI instead of component so you may want to stick with component for the 1080 output from the Comcast sTB unitil you get a 3D BR diisk player and then use your 1.4 cable for that.
All signals over Coax are SD 480i resolution so you don't want to use coax
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post #3 of 12 Old 05-17-2010, 11:15 AM
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I agree with the post above. You Digital Box must be receiving something from the TV that it doesn't understand. Same thing as Digital Signals going into an Analog Only TV. It won't know what to do with the digital signals. I would use a component video cable to connect your box to your tv. You will still get 1080i output & the problem would go away when you stop using the hdmi cable. The Component Video Cable's are $10 to $15 compared to $20 or higher for a single HDMI Cable.

Almost forgot, Don't forget to connect the Red & White audio cable to get sound from you box.
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post #4 of 12 Old 05-17-2010, 12:44 PM
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On a side note, I recommend using Monoprice or Blue Jean Cables...(see ads and links for both on this site) for ALL your cables...yes, the prices are MUCH lower, and yes the cables work fine.

Peachtree City Golf Cart Rider
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post #5 of 12 Old 05-17-2010, 12:58 PM
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With the HDMI cable attached, try setting the video output of the cable box for "fixed" 1080i.
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post #6 of 12 Old 05-17-2010, 01:12 PM
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I agree with Ratman, the effect you're getting is probably from switching to a channel that is a different resolution so the TV needs to resync.

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post #7 of 12 Old 05-17-2010, 08:26 PM
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Quote:
Originally Posted by mjones73 View Post

I agree with Ratman, the effect you're getting is probably from switching to a channel that is a different resolution so the TV needs to resync.

Yep, exactly what I was thinking. You need to set the cable box to ONLY output 1080i, that ay when you switch from a 480 or 720 channel, the tv doesnt have to reset the resolution. My tv will do this once in a while if i dont have the cable box set to 1080i only.
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post #8 of 12 Old 05-18-2010, 07:03 AM - Thread Starter
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Thanks for the tip! You guys nailed it! Setting the cable box to only 1080i stopped any of the between-channel flicker.

The follow-up question, I have is: does this mean I have a defective TV set? One that is not able to handle resyncing well? This does not seem to be a common problem and certainly the Comcast level 1 rep didn't have any clue. If it is a problem with the set, I'll probably get it exchanged, since I've only had it less than a week. The cable box, BTW, is a Comcast RNG 110 and my TV is a 50" panasonic VT 25, if that matters.

thanks again,

- Frank
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post #9 of 12 Old 05-18-2010, 07:41 AM
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No there probably isn't a problem with your TV. Most TVs will have a slight delay/flash when switching resolutions.
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post #10 of 12 Old 05-18-2010, 09:01 AM
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As long as your cable box does a better job of upscalling the 720p(ABC, FOX, ESPN-HD) channels to 1080i then your VT25 does (which I doubt) using only 1080i instead of pass through mode is a no brainer solution.
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post #11 of 12 Old 05-18-2010, 02:19 PM - Thread Starter
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Quote:
Originally Posted by walford View Post

As long as your cable box does a better job of upscalling the 720p(ABC, FOX, ESPN-HD) channels to 1080i then your VT25 does (which I doubt) using only 1080i instead of pass through mode is a no brainer solution.

So is it better to use the component-out solution, and let the cable box output what it wants then? Using old component out cables also stopped the flickering, though I was surprised to hear they were essentially as good as the HDMI cables.

- Frank
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post #12 of 12 Old 05-18-2010, 02:53 PM
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Stay with the HDMI cable and fixed 1080i if all works well now.

Don't let the three 720p channels and "which has the better upscaler" cloud the issue at hand. You still have a ton of 480i and 1080i channels to contend with.

Or... use what works/looks better to you.

You could use the same argument that the quality using component vs. HDMI depends on whether the D/A converter is better in the cable box or the TV.
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