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Topic:
IR Interference from LCD HDTV Backlight
This thread has 10 replies. Displaying all posts.
Post 1 made on Monday February 20, 2006 at 16:13
Peleliu
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2
I have a Panasonic TC-32LX50 LCD HDTV and a Scientific Atlanta 8300HD DVR cable box. After turning on the TV, I have no control from the remote until after 15-30 seconds. I found out from another forum that the backlights in LCD monitors produce a lot of IR noise when first coming on. This bounces off the walls and back into the cable box IR sensor and overrrides the Time Warner remote control (Universal Electronics Atlas DVR/PVR 5-Device Universal Remote Control) IR signal. I can't change anything on the cable box until the IR noise dies down. Then it works fine. I have verified this by covering the TV screen with a blanket after which I can change the channels, etc. Since this only happens upon TV warm-up, it is difficult to diagnose, so I have to immediately turn the TV off to try different fixes.

To fix this it has been suggested that I put several layers of masking tape over the cable box IR sensor, turn down the TV backlight, reposition the TV relative to the cable box, or switch to an RF remote with an IR repeater mounted on the front of the cable box. I tried all of these but the RF remote with no luck. Scientific Atlanta doesn't respond to consumers technical questions directly and refers questions to the cable company. This is well beyond the ability of Time Warner. Can anyone suggest anything else I can do to overcome this?
Post 2 made on Monday February 20, 2006 at 16:28
Ernie Bornn-Gilman
Yes, That Ernie!
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On February 20, 2006 at 16:13, Peleliu said...
I have a Panasonic TC-32LX50 LCD HDTV and a
Scientific
Atlanta 8300HD DVR cable box. After turning on
the TV, I have no control from the remote until
after 15-30 seconds.

The TV remote or the cable remote? It often happens that TVs won't respond right away, especially if there is a lamp to warm up. But LCDs shouldn't have that problem unless they are LCD rear projectors.

I found out from another
forum that the backlights in LCD monitors produce
a lot of IR noise when first coming on. This bounces
off the walls and back into the cable box IR sensor
and overrrides the Time Warner remote control
(Universal Electronics Atlas DVR/PVR 5-Device
Universal Remote Control) IR signal.

That's pretty interesting. Are you turning on the TV, or the TV and the cable box?

I can't change
anything on the cable box until the IR noise dies
down. Then it works fine.

Okay.

To fix this it has been suggested that I...blablabla
I tried all of these but the
RF remote with no luck.

Uh, what exactly was that last sentence? When you say you had no luck, you mean you moved the TV with relation to the cable box, say, to another room (it's easir to move the cable box for this trial)?

If the TV is spraying IR all over the room, the only one of those solutions that might help would be the layers of masking tape, but they might kill IR reception, too. If the TV puts out the same frequencies of light as the remote, blocking one will block the other.

Can
anyone suggest anything else I can do to overcome
this?

Yeah. Wait a few seconds.

Think of it as high technology that has to get all its voltages and such set up before you can use it. On integrated remotes like the RTI Ts+, I have used a screen that says "Please wait while the system turns on" with up to a twenty second delay for everything to settle down.

Alternatively, don't turn off the TV, move the cable box to another room and use an RF link, or get a new blanket plus an electronic blanket lift. I personally like that last idea the best. It will drive your cat nuts, though, when you turn the TV on.
We can't give you a good answer, or maybe any, without the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
OP | Post 3 made on Monday February 20, 2006 at 19:51
Peleliu
Lurking Member
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February 2006
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On February 20, 2006 at 16:28, Ernie Bornn-Gilman said...
The TV remote or the cable remote? It often happens
that TVs won't respond right away, especially
if there is a lamp to warm up. But LCDs shouldn't
have that problem unless they are LCD rear projectors.

I was referring to the remote that works the cable box. With a cable box, the TV remote is secondary, usually only for set up. Apparently LCD's have the problem because of the backlight lamp that provides the illumination for the LCD panel. It requires a higher voltage during start-up, so IR emmisions then are high.

That's pretty interesting. Are you turning on
the TV, or the TV and the cable box?

I'm turning on both.
Uh, what exactly was that last sentence? When
you say you had no luck, you mean you moved the
TV with relation to the cable box, say, to another
room (it's easir to move the cable box for this
trial)?
I oriented the TV so the TV is at an angle to the room walls. The ratioale was that the IR emissions wouldn't bounce directly off the wall opposite the TV and back into the cable box which sits above the TV.
If the TV is spraying IR all over the room, the
only one of those solutions that might help would
be the layers of masking tape, but they might
kill IR reception, too. If the TV puts out the
same frequencies of light as the remote, blocking
one will block the other.

Remember that the remote is an active IR device and the IR from the backlight is reflected off walls so the stronger remote signal should override the weaker reflected IR noise if the geometry could be figured out. I haven't been able to make that work though, because the front of the cable box has a large window. So I would have to tape over the whole display. I'll keep experimenting.
Post 4 made on Wednesday February 22, 2006 at 02:00
Ernie Bornn-Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
22,891
On February 20, 2006 at 19:51, Peleliu said...
the IR from the backlight is reflected off
walls so the stronger remote signal should override
the weaker reflected IR noise if the geometry
could be figured out.

I guess. The problem as you are experiencing it is that the reflected signal is strong enough to interfere with the remote control signal. What makes you think the reflected signal is weaker than the remote control signal? If the reflected signal is much weaker than the remote signal, the layers of tape might work...you should just try it out. Heck, it's a cheap fix.

I once accidentally cured a similar problem with blue painter's tape that I actually thought would kill all IR but happened to pass it pretty well.

I haven't been able to
make that work though, because the front of the
cable box has a large window. So I would have
to tape over the whole display. I'll keep experimenting.

You could put some actual black plastic over the window around the sensor and cut down the amount of window that will transmit IR through to the sensor.
We can't give you a good answer, or maybe any, without the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 5 made on Wednesday February 22, 2006 at 10:19
Spiky
Founding Member
Joined:
Posts:
May 2001
2,288
I have the same problem with some fluorescent bulbs in my house. Although my remote is usually strong enough to overcome it. But I can see the IR output when the lamps are first turned on since my Xantech IR receivers' light goes on, showing IR activity. Fades after about the same 30 seconds.

Waiting works just fine.
Post 6 made on Friday February 24, 2006 at 20:47
arielav
Long Time Member
Joined:
Posts:
September 2005
14
You are right that the LCD and Plsama TV's emit a lot of noise that can confuse an IR remote. Other problems might be the environment you have your equipment placed in.

Do you have mirrors in the room? Do you have bright colored walls. Do you have exposed glass. These can all cause the signal to bounce off the surface and repeat again and again and confuse the cable box. Some lighting can also cause problems like florecent lights and halogen lamps.

I install a lot of equipment in cabinets to hide the electronics for my clients. I use a plasma proof target eye. It plugs into an IR repeator system it is powered by a 12v power supply and emitters are pluged into the repator system. You attach the emitter onto the sensor on your components (cable box, other components) and the commands are repeated to the component you want to control.

I use Niles, Audioplex and Xantac. You might want to check out this website:

[Link: nilesaudio.com]

Niles has 2 prepackaged kits the emitter should be attached to the component (in your case the cable box) also included in the kit is a cover to mount over the emitter and will block out the IR sensor of the cable box so only the emitter is sending the signal to the cable box. You might need to reposition the the IR target depending on your enviroment. Keep in mind the section above regarding your environment.

Most of my work is in NYC appartments so a wired system works best for me instead of RF remotes.
Post 7 made on Tuesday March 17, 2009 at 11:52
newtv52
Lurking Member
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Posts:
March 2009
1
I know it's been a while, but have you found a solution for this problem? I am going through the same issue right now, but my delay time is about 4-10 minutes.
Post 8 made on Wednesday March 25, 2009 at 17:54
Ernie Bornn-Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
22,891
Search for this problem in the Custom Installers' Forum. It's been discussed there a lot. I'm not sure what search terms to use -- you probably found this thread by a search, after all.
We can't give you a good answer, or maybe any, without the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 9 made on Thursday August 20, 2009 at 10:37
pwnosaur
Lurking Member
Joined:
Posts:
August 2009
1
Hey everyone, I just bought a 42" LCD and had the same issues. HOWEVER! I was able to find a work-around. I got some electrical tape and covered 90% or so of the IR sensor on each of the devices I use and everything works like a charm. The obvious: it blocks out most of the random IR interference from the TV. Also, make sure you position the tape accordingly for optimum reception. Took me a few trys but, I finally got it to work just about anywhere in the room.

P.S. I registered just to post this solution so, I hope it helps :)
Post 10 made on Thursday August 20, 2009 at 16:03
Ernie Bornn-Gilman
Yes, That Ernie!
Joined:
Posts:
December 2001
22,891
Thanks for the solution. You'll find more on this in the Installers forum, too. Sometimes the tape doesn't work and other things need to be done.

Welcome to the site.
We can't give you a good answer, or maybe any, without the make and model of everything.
"The biggest problem in communication is the illusion that it has taken place." -- G. “Bernie” Shaw
Post 11 made on Wednesday April 7, 2010 at 20:56
pepe49
Junior Member
Joined:
Posts:
April 2010
1
hey i have a tc-32lx50 and it has this red, blue, green and white vertical lines on the screen and i wanted do know what is wrong with it. like everything else work its just those line on the screen. what do i have to fix?


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