Panasonic TH42PX80UA Tuner Problem - AVS Forum
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post #1 of 5 Old 04-29-2012, 07:16 PM - Thread Starter
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In my area, Comcast just completed removing the analog channels from their system. I rescanned all the channels, the TV stopped at 55%. I tried scanning only the digital channels it stops at 10%, without finding any channels.

I tried disconnecting the cable input, then it scans all the way through without stopping. Hook the cable back up, same results as the first scan.

Now the bad part, before the rescan I was receiving the clear QAM channels, now I cannot receive them even by manually entering them.

I did a reset from the remote, disconnected AC power for a few hours, still no QAM.

It acts like it knows the QAM signals are there, because that is what makes it hang during the scan.
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post #2 of 5 Old 04-30-2012, 07:37 AM
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Comcast had also recently removed all the analog channels from my area.

My TH-42PX80UA was able to scan and find clear QAM channels, but very few are actually worthwhile to watch. Most seemed to be advertisements for On Demand.

I wouldn't be surprised if Comcast produced a rogue QAM channel to fool tuners, in the hopes that a set top box would be rented instead.

That which may be known of God is evident within man, for God has shown it to them, so that they are without excuse. (Romans 1:19-20)
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post #3 of 5 Old 04-30-2012, 08:26 AM
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Quote:
Originally Posted by sichejo View Post

In my area, Comcast just completed removing the analog channels from their system. I rescanned all the channels, the TV stopped at 55%. I tried scanning only the digital channels it stops at 10%, without finding any channels.

On some of my installs (including my own) it did look like the scan stopped early and hung, but when i left it sit like that it eventually completed the scan. Sometimes it takes more than an hour.

At my SIL's house and other friends in West L.A., Comcast doesn't provide a signal from the wall (they never have) and every TV must have it's own cable box. Over the years i've tried scanning analog tube TVs as well as digital tube TVs and various Flat Panel TVs but there simply is no signal from the wall - it's scrambled. Maybe your Comcast network changed to this type of system?

BTW, when i run a channel scan, i put the TV in Standard picture mode and turn the Contrast all the way down to avoid getting IR from the scan progress bar menu thingy.


Quote:
I tried disconnecting the cable input, then it scans all the way through without stopping. Hook the cable back up, same results as the first scan.

This must be done after every failed attempt as it's the only way to clear the tuner after a corrupted scan.

Randy
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post #4 of 5 Old 04-30-2012, 11:01 AM - Thread Starter
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I have a 32" Panasonic, it scanned fine. I also have a 19" Sanyo, it was ok.

Tom, I was thinking along the same lines as you about an intentional or not, bad QAM signal causing the problem. Since it will complete a scan without any signal input, and it only hangs during the digital portion of the scan.

If there is a bad signal causing the problem, I could use a spectrum analyzer and find the lowest channel, and get a trap to eliminate it. During the scans, it never finds a channel. So it seems like it would be caused by the lowest channel.

But, why can't I enter a QAM channel directly? It displays "channel not available (no signal)" That is weird too...

It does scan correctly for the OTA channels.

Thanks
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post #5 of 5 Old 05-10-2012, 05:55 PM - Thread Starter
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A follow up on the scanning problem.

I disconnected the cable tv input, and started the scan. After the digital channel scan cleared 10%, I re-attached the cable line. It continued to scan to 100%. It works fine now.

As suspected, there must be a digital signal the tuner does not like. I will have to get the spectrum analyzer out of the truck and find a "N" to "F" adapter. I will get a trap or a CEF to eliminate it.

I'll post what channel it does like when I find out.

Thanks
John
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