Home audio & video forum: IR interference from LCD TV

I did not measure the noise. This conclusion is based on my chat with technical support at dish network and google search. I didnt use camcorder to see any noise.

Some newer hi-end LCD TVs are now using LED backlighting versus more conventional flourescent backlights. I guess the change allows for more control over black levels and lower power consumption.

Apparently when these sets are first turned on from a cold condition the LED backlight power is raised - probably to heat the screen. On my Samsung LN46A850 this lasts about 5 to 10 minutes. After that the level drops and my remote for the Scientific Atlanta DVR becomes useable again.

To Bob's point, this can easily be seen using a more recent video camera, especially one with night vision. During the wee hours a few mornings ago, while it was still dark (I didn't want any sunlight interference), I set my video camera to nightlight and turned on the TV which was at room temperature. Sure enough the screen glowed bright white in the viewfinder. As the picture came on I could barely make out the video image over the bright white. In about 5 to 10 minutes the white background subsided allowing me to view the video image perfectly in my camcorder viewfinder. At that time the DVR remote started working again (I had been checking this periodically while the TV was warming). Camcorders are sensitive to IR wavelenghts invisible to the human eye and display this as white light on the viewfinder which makes them perfect tools to show this problem.

None of this is rocket science and I'm sure the Samsung and other manufacturer's engineers know all this. The question now becomes whether Samsung and the other manufacturers using LED backlights can devise a firmware update that allows us to turn off the warmup cycle or lower the intensity level so that while it may take longer to warmup the TV doesn't flood the room with IR wavelenghts that blind our DVRs and other IR driven equipment.

Please note that this is not just a Samsung issue. Others using LED backlighting have the same problem to varing degrees.

Paul

I used to have a Samsung LCD which would show up on my MS mediacenter IR receiver
all the time. I think the problem is that the backlights in a LCD set is driven by an a high voltage inverter, so the backlight is in effect modulated by the frequency that the inverter runs at. This can be seen with the naked eye , but it gets picked up by IR receivers. I now have a gorgeous Samsung LED tv which doesn't put out any interference
as LED's are driven at a much lower voltage and no need for an inverter.

btw, any one interested in a free voice operated remote control , theres a giveaway at
http://www.amuletdevices.com/index.php/General/45-Giveaway.html

i do not deal with dishnetwork nor do i know how enough to give a good answer....

but arent the remote controls on the hd boxes for dishnetwork radio frequency instead of IR? (i guess it might depend on which one you have. cause i know for sure they have a system where all you need is 1 box for pictures on 2 different tv's)

I havent found a solution yet, the remote starts working after half hour or we keep it quite close to IR receiver and it works..thats the only workable solution i have found.

I've been a Comcast Technician for 2 1/2 years and I thought I've seen it all. Yesterday we got a memo from our supervisor regarding this problem. It stated a customer purchased a Sharp Aquos and we installed a Motorolla DCH HD Box. The STB remote would not function with the TV on. The tech discovered a feature on this TV (OPC) wich automatically adjusts contrast and brightness to adapt to room lighting. This feature interferes with some set-top IR sensors. The tech resolved the issue by disabling this feature. My last trouble call today was the same issue with a Panosonic TH-58PH1OUKA. I swapped the STB twice and the remote 3 times. Then I noticed that this model has a similar feature as the Sharp, called C.A.T.S. (Contrast Automatic Tracking System). Ok, this is where it gets baffling. The remote functions without a hitch when the feature is ENABLED! Sharp's model has no IR interference when DISABLED. So after 2 hours of troubleshooting I left the customer with a functioning DVR/Remote and a much dimmer picture, because if you manually change the contrast/brightnes, the set automatically enables C.A.T.S. by defult. Panosonic Cust Serv advised me to leave it enabled. There's going to be a hot debate at the shop in the morning on this topic.

Solved the IR conflict. Easy fix. We had an unused IKEA component cabinet with smoked glass front. Placed the cabinet to the left of the LCD TV and put the set-top box inside. Joy!! Now have a cable box that works with the Comcast remote! Good luck to you all!

I have the same problem with the Samsung LN40A650. Called Samsung tech support and they acted like they never heard of the problem. Anyway, its definitely an IR problem caused by the TV.

I see that Amazon has the Next Generation Remote Control Extender. Looks like that should solve the problem although I haven't tried it.

Good luck.

Just invested in a Samsung LE52B755 and was confronted with massive ir problems. By turning off the energy saver the problem was gone. HALLELULJA!!! What would one do without internet. Thanx again. Fred

I had the same problem. I bought a "Wired IR Remote Receiver/Repeater (Kit #RRIC @ $29.95 and 100VAC Power Adapter #AC125 @ $9.95) from Ramsey Electronics (www.ramseykits.com 800-446-2295. I assembled the kit. The face of the box has a IR signal receiver and a (Green LED) that shows IR activity received by the box. The unit then transmits, by wire, the received IR signal to a white LED tip that you place in front of (on) the DVR IR window using black electrical tape to hold it in place. The box will receive your remotes signal and place it directly into the DVR IR window. This signal is much stronger than the stray IR from the TV. IT WORKS GREAT. It is interesting to see the green LED on the box start to flicker when you turn on your TV and other lights in the room. Interfering IR is everywhere but as you know the LCD TV generates a lot. If you have any questions about my fix don,t hesitate to email me. Also Ramsey will talk to you about the kit assembly if you have problems.

I'm considering using the Hotlink remote control booster, http://hot-link.com/pages/products.cgi?mrchcatid=1&mrchid=2

The components, cable box, etc. will be in a closet behind the wall mounted LCD TV. The sensor can be placed anyway but I'm thinking behind the TV facing the wall. The theory is the it'll amplify the IR beams. I'm thinking the transmitted IR should then be strong enough to over ride the emitted IR from the set...any thoughts as to the sensor placement or other suggestions.
Thanks

Hey Tom,

I'm having a similar problem with my new Dish HD remote and the dish tech told me this could be a prob with the IR. However after reading this blog, I wanted to turn the energy saving option to low of off on my Toshiba, but could not find that feature/option anywhere..Can you tell me where if on tv or tv remote will I see the option to turn this off??

Ty
Vaas

I have a sharp aquos and a shaw HDPVR and had the same problem until I realized it was my TV causing the interference.

You don't need a 1/8 IR repeater thing. (one came with my box)
You don't need a ridiculus cardboard tube.

You just need a piece of tape (scotch will work).

There are usually two infrared eyes on the front of a cable/satellite box. One to recieve and one to transmit signals. Be sure to tape over the one that transmits. ( a little experimenting can determine this.) Through a small amount of trial and error you should have your remote working perfectly in no time.

What an informative post. I have a samsung ln52a650 and motorola comcast hd box. Initially my remote always took a minute or two before it worked consistently. I was playing around with my tv settings at the time so I didn't notice a correlation. Recently my hd box would barely respond to the remote. After reading this post I remembered I changed the ENERGY SAVING settings to med or high. Switched it back to low and now everything is OK. Never would have thought, thanks for the info!!!