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TV changing channels or volume by itself, where is the problem?

Posted by 123onlineservices on October 26, 2012 at 1:20 AM Comments comments (3)

This article is about a not very common yet definitely annoying problem that can develop in any TV - LCD or plasma - and a basic troubleshooting guide to help narrow it down to a particular module.

 

It was prompted by a recent experience followed by a user question that has just arrived.

 

Question: 

Dear 123 Electronics Repair,

I had you service the Y-SUS board in my HP PL4260N and it works fine.

 

I am having another problem with the TV now and was wandering if you have heard of it and if so how would I solve the problem.

 

The tv will start changing channels on its own along with volume and flash the menu.I ruled out the remotes and covered the ir, disconnected all cables and it still does it.

 

Do you have any ideas what it could be?

Answer:

The described problem of random channel change or volume increase or volume decrease can happen on any TV and I have seen it happen on different kinds of TVs.

 

There may be some that may be more prone to it - a common production defect is always capable of causing something like it - but I am not aware of any particular TV model where this is a known mass problem, including the HP PL4260N.

 

The good news is that on all TVs the troubleshooting process is relatively similar and also relatively simple.

 

The TV - be it LCD, plasma, LED, most likely projection TVs as well (although we don't do those) - can receive a command to change volume or channel in two major ways - the IR sensor or the on-unit navigation control, which in most TVs is in a form of several buttons.

 

Both these sources travel , usually independently from each other, to the main board where they are processed by the TV's "brain", the main board's micro controller.

 

Which means that the distortion can come from:

1) the TV's IR control unit including all the way to the main board

or

2) the TV's manual navigation unit, including wires all the way to the main board

or

3) something on the main board itself; because of the way the IR and the buttons modules operate this is more likely to be something in the navigation button's circuit than the other one, but either way it would be something on the main board.

 

To rule out the IR board you would want to just disconnect it from the main board. You can often do that at the plug on the IR board itself, but it is usually easier to just trace the cable from it to the main board and disconnect it there.

You can power on the TV and disconnect it then or you can disconnect it and power on automatically.

Either way you are trying to see if disconnecting the IR board will cause the volume or channel change to stop.

 

You do the exact same to rule out the buttons navigation board. Disconnect and power on through remote (of course IR board will have to be connected) or power on and disconnect from the main board.

If volume increase (or decrease) stops or channel flipping (or menu activation) stops, then it's something on the board or cable.

Literally two weeks ago I saw for the first time in my life a volume up button which has failed and had a constant 50 ohm resistance, resulting in a constant "vol+" response from the TV. TV owners said they don't ever use the button which is believable since almost everyone these days uses a remote. And yet it has failed.

 

At least once before I have seen the cable from the buttons panel to the main board get squeezed by and subsequently cut by the TV's bezel. I have also seen that same problem in other Chinese devices. Good companies - I think of Philips - design wire paths inside the body to prevent things like those from happening.

 

Anyway, if you rule out both of those then the problem is in the main board.

 

I have seen at least one case where a resistor has failed, near the buttons connector, and was causing the problem. Most if not all modern TVs do not have dedicated wire for each button on the panel; instead, they use an analog to digital converter on the main board to convert resistance to digital level.

Buttons on the power board are simply resistors that get connected to a chassis; different buttons connect different resistance values, the main board converts that to a digital number and the main board maps a number to a function.

Stands to reason that any significant impedance (resistance) change in the circuit will lead to misfire.

 

Sometimes the problem may not necessarily be a resistor; it may be an active component, i.e. the ADC (analog to digital converter) itself.

 

Troubleshooting the power board is beyond the scope of this article.

 

Hope this helps!

Cloaking Techniques Could Help Future Electronic Devices

Posted by 123onlineservices on October 13, 2012 at 10:55 AM Comments comments (0)

Cloaking Techniques Could Help Future Electronic Devices


The power of cloaking mechanisms could eventually lead the way for developing more efficient thermoelectric devices and new kinds of electronics. MIT researchers applied the idea of harnessing the cloaking mechanisms developed to shield objects from view, to the movement of electrons.Previous work relied on metamaterials made of artificial materials with unusual properties. The composite structures used for cloaking cause light beams to bend around an object, and then meet on the other side.


“We were inspired by this idea,” said Gang Chen, the Carl Richard Soderberg Professor of Power Engineering at MIT, who decided to study how it might apply to electrons instead of light. The team, writing in the journal Physical Review Letters, said they modeled nanoparticles with a core of one material and a shell of another. Rather than bending around the object, the electrons actually pass through the particles.


Computer simulations show that the concept appears to work, and now the team will just try to actually build devices to see whether they perform as expected. “This was a first step, a theoretical proposal,” said MIT graduate student Bolin Liao. “We want to carry on further research on how to make some real devices out of this strategy.” The initial concept was developed using particles embedded in a normal semiconductor substrate. Now, the team would like to see if results can be replicated with other materials.


The team’s initial impetus was to optimize the materials used in thermoelectric devices. These devices require a combination of characteristics that are hard to obtain, but simulations show this electron-cloaking material could help meet these requirements. Simulations used particles a few nanometers in size, matching the wavelength of flowing electrons and improving the flow of electrons at particular energy levels by orders of magnitude compared to traditional doping strategies. The team said that this might lead to more efficient filters or sensors. Chen says as the components on computer chips get smaller, “we have to come up with strategies to control electron transport.”


The concept could lead to a new kind of switch for electronic devices, according to Chen. This switch could operate by toggling between transparent and opaque to electrons, turning a flow of them off and on.“We’re really just at the beginning,” Chen said. “We’re not sure how far this is going to go yet, but there is some potential” for significant applications.



Source: Lee Rannals for redOrbit.com - Your Universe Online

 

 

Polycom, Microsoft, Take on Cisco in Video Conference Technology

Posted by 123onlineservices on October 9, 2012 at 10:30 PM Comments comments (0)

 

"As Polycom introduces a wide array of new video conference technology, the company says its partnership with Microsoft presents a strong challenge to Cisco Systems.

Polycom introduced a number of new video conference systems on Oct. 8 and a Polycom executive says that his company, in partnership with Microsoft, has been gaining market share at the expense of rival Cisco Systems.

Polycom introduced several new systems based on more than two years of research to widely revamp its product line, all of it now supporting the emerging scalable video coding (SVC) standard to deliver high-definition video across networks.

Announcements include the launch of the new Polycom RealPresence CloudAXIS Suite, which enables the user of a Polycom video conferencing system to connect to one-call participants using other systems such as Microsoft Skype, Facebook, Google Talk and others. Also, the RealPresence Platform has been enhanced to support the open standards-based SVC and deliver a three-fold increase in high-definition (HD) multipoint video capacity.

Improvements have also been made in the user experience on Polycom systems including Polycom SmartPairing, which allows a user participating in a video conference via a tablet computer to transfer the video call to a room-based system with a swipe of a hand on the tablet’s touch-screen. The tablet then becomes the remote control for the room system, letting the user access the corporate directory to add people to the call.

These and other new products and services enhance the usefulness of Polycom systems, including those that integrate with Microsoft unified communications technology such as Microsoft Lync and SharePoint, said Jim Kruger, senior vice president of product and solutions marketing at Polycom.

“With Microsoft, we have a high win rate against Cisco,” said Kruger, adding that Polycom already has 44 different products that interoperate with Cisco, and with this latest array products that number hits 50.

“A Polycom customer can have a Lync client running on their desktop computer and be able to connect into the RealPresence conferencing platform and make use of the greater multipoint capabilities in the upgraded system,” he said.

The difference between a Cisco system and a Polycom/Microsoft system serves as another example of the ongoing debate in IT between an end-to-end system versus a best-of-breed platform.

“Cisco’s strategy is ‘Buy from one vendor; we do everything end-to-end and if you have anything else on your network, rip it out and replace it with Cisco because we’re the best,’” Kruger said. “With Microsoft and Polycom, it’s more about best-of-breed, having options and choice because you have a choice beyond Polycom. If you want to use someone else besides Polycom in a Microsoft environment, you could.”

Offering to integrate with other video conference equipment and Microsoft platforms such as Lync is part of the reason Polycom says it has gained share in the market for video conference systems endpoint equipment at the expense of Cisco.

For the second quarter of 2012, Cisco’s share of the market was 44.6 percent, still the market leader but down 6.3 percent from the previous quarter and down 3.3 percent from the year-ago quarter, according to Synergy Research Group. Polycom was second with a share of 30.7 percent, up 4 percent from the previous quarter and up 2.6 percent from the year-ago quarter, according to the Synergy Research market study. Other vendors, including Huawei, Logitech, Vidyo and Avaya, each held market share in the single digits.

In a blog post Oct. 8, Thomas Wyatt, vice president and general manager of the Collaboration Infrastructure Business Unit at Cisco, wrote that Cisco is committed to the proliferation of standards adoption and that it is a member of standards bodies such as the Open Visual Communications Consortium (OVCC).

“We have always been firm believers that video calling should be as easy and ubiquitous as making phone calls,” Wyatt wrote.

Cisco has often pursued a dual strategy in technology development of supporting standards creation while simultaneously developing proprietary technology that would differentiate itself from its competitors."

Source: http://www.eweek.com/networking/polycom-microsoft-take-on-cisco-in-video-conference-technology/ by Robert Mullins


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