Trying to find LED Backlight for model LD-2655VX

[keeney123]

Does anyone know where I might purchase led backlights for Westinghouse model LD-2655VX LCD TV? There are two sets of 25 leds each side or total 50 leds. There is a connector on each side of the TV and I believe the connectors to be bad as I have cleaned the contacts. Everytime I tap the connector the lights light up or go out. This is happening with both connectors.

[MagicSmoke]

Re: Trying to find LED Backlight for model LD-2655VX

You might try ebay. I had luck asking a seller that had other parts for a certain tv if he had the backlight strips. He did have them but not on auction.

You might try a resolder on the led strip connector pins it may have a cold solder joint. Or the wires to them might be broken inside the insulation.

[lookimback]

Re: Trying to find LED Backlight for model LD-2655VX

I recall one of those Westinghouse TVs having issues with the ribbon cable being pinched and shorting where it wraps around to the connector. Be certain that isn't the issue.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

I recall one of those Westinghouse TVs having issues with the ribbon cable being pinched and shorting where it wraps around to the connector. Be certain that isn't the issue.

The cable is not pinched, but your post caused me to take a closer look. I think it is the connection between the end of the cable and the connector to the led strip. They put one of those blue pull tabs on the end of the cable, but it is to the very end of the cable so it actually goes all the way into the connector. This is putting to much pressure down on the cable contacts causing slight bends in the cable contacts at different points. I think that is why when I tap the connector it vibrates enough to move the cable enough to connect or disconnect and the heat of the metal back strip to the LEDs is another factor on solder joints stressed from expansion.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

I modify there design and was able to get all the LED's working. I change the path the ribbon cable took so that the cables had some slack. I tape them down so they would be out of the way. I cut out a small piece of the metal so the LED strips could be put in and taken out without having to unplug them. I took the thermal tape off the back of the LED strip and replace it with thermal silicon paste. Tomorrow I will get high temp silicon to fasten the LED strip securely. I tape the LED strip connector to the ribbon cable so neither would move and then I tape the cable to the metal part of the panel to keep connector and ribbon cable protected and secure.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

Seems that there is another problem causing these LED backlight to go off intermittently. They do not all go off intermittently just some. I contact Westinghouse because their version v.1 upgrade was unavailable on their web site. After the customer support did not contact me I wrote to their Public relationships and then I was given a link to their version V.1 upgrade. After I installed this program it seem more stable. It did cure the screen going black and then coming back on and then going black, but I still have the LED problem. I could buy a board for $34 plus shipping from Jimmy, but I do not think this TV is worth that. It seems to me to be an engineering failure. Perhaps that is why they discontinued it.

[tibimakai]

Re: Trying to find LED Backlight for model LD-2655VX

You should share that link, with everybody.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

You should share that link, with everybody.

This is the link for the upgrade to firmware of Westinghouse LD-2655VX the upgrade version is V.1 http://1drv.ms/1zXMDlI

Instruction on how to upgrade the tv can be found on Westinghouse site under support for TV's LED up to 28"

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

Does anyone have a schematic for the LED light strip that goes to this TV? The LED Strip is from Manufacturer Kenmos with the following numbers 84420601 00- L, FHt-1011, HK2T51A3P-01A that is for the left side of the TV where the right side is 84420602 00-R, FHt-1011, HK2T51A3P-02A.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

You should share that link, with everybody.

Here is the instruction site for the link

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

The answer to this problem would be to get LED Strips that have their own linear power supply that has a rheostat to control the intensity of the lights. If lighting conditions change one just adjust a rheostat. Replacement would be easy. Can not find this at least not made in any other countries expect in Asia. Getting data specifications from Kenmos in Taiwan is next to impossible. To me the LED connector on the LED Boards do not match the ribbon cable that is being use. Where the connectors on the main board are the correct connectors. They flip open and one inserts the cable and then one locks down the connector. The LED board connectors are ones that the manufacture had to place a hard plastic tap to the very end of the ribbon cable because the cable itself would just fall out of the connector. The problem comes when forcing this flimsy ribbon cable into the LED connector, it actually damages the connector a pond insertion. The other problem is each cable to the LED's are 2.5 feet long which makes the current path from and to the LED driver IC 5 feet for each path of twenty circuits. The IC is controlled by software which also measures the conditions of temperature and current and voltage coming into the LED driver chip and adjust the output of the LED driver chip accordingly. Dimming is also controlled by a pulse width modulator within the same LED driver chip. The LED driver chip has one voltage output to the LEDs and ten separate paths that return which are monitored by the current. My TV has been an intermittent problem that has been occurring for an unknown time. I am at present contacting Molex to see if they have a ribbon cable replacement and LED connectors replacement. Will post their reply.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

Molex does not have a cable that will work. I find this amazing. I guess one is suppose to throw the whole unit away because the backlights do not work correctly.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

I then ask Molex if they know where I could buy a cable that was made of quality and they said no they did not know. This is Amazing to me because they are in the business of making and selling cable and connectors and they can not tell me where I might get a cable and connector to get these LED backlights to work. Molex has been a leader in cable and connectors for many many years. I will not buy from them again. I think when my TV goes I will also, not buy another TV. This is the only way I know of to protest this type of behavior.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

It seems each of these cables have a 0.016" pitch and total width of 0.230" the connector contacts are about 0.010". One cable is 30" long and the other about 24 inches long. So the round trip of the voltage signal is 60" on the 30" long cable and 48" for the other one. The total thickness of the cable with plastic insulation is 0.005", so the connector in the cable is very tiny which means a higher resistance. These are rough measurements as I used a 6 " vernier calipers to take the measurements. Also, the connectors have a width for a 0.025 thick cable to go into it. This is why they glued the blue plastic piece on the end of the cable. Super glue will not stick to the cable. I would try a solvent like PVC cement used on irrigation pipes or acetone. That is if you want to cut the cable, scrape the insulation off and then re glue the blue plastic piece back in place.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

This is a letter I sent to Westinghouse Customer Service. Also, I have attached the chip data that drives these LEDs.
Dear Al,
The firmware update did cure the problem of the unit going off and on, but it did not cure the LED light problem. Here is what I have found. After trying to get information from the Kenmos site and being unable to get any information. I contacted Molex connectors and asked if they had a replacement for both the connectors and the ribbon cable. Their engineering sales people simply said they have nothing to replace them and they did not know where I can get them. I took some measurements of you connector and ribbon cables. The connectors on the board have room for a 0.025" cable, but the cable that was in the unit is only 0.005 thousands thick. This is why the blue plastic pad was glued onto the end of the cables. This was alright on the connectors on the board, but the connectors on the LED strip had damage to the ribbon cable connectors. The ribbon cable is less than 32 gauge wire. The long cable in the TV was 30". If the cable was 32 gauge it would have 0.8 ohms of resistance. Then there is connector resistance and frequency resistance known as the skin effect. After not being able to find a replacement I decided to cut off the connector leaving the leg of the connectors to solder too. What I have found out so far is most of the connector solder points were not even soldered to the board because when I cut the connectors leads they just fell off.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

On top of everything else I found that the boost fet inside of the MC34844 is shorted. I do not know the internal design of this chip other than the block diagram. The symptom was sometimes all of the lights worked and then just a few. Seems like Pandora's Box.

[keeney123]

Re: Trying to find LED Backlight for model LD-2655VX

Last post by me on this subject. This is another letter to Westinghouse.
Dear Al,
I know you do not have internal part. What I said in the last letter is a suggestion to pass along to your management. As this is a problem with these TV's. I have had over 244 people looking at my post over this particular TV. It would do your company good credit to help resolve this problem. I believe what happen to this TV is that because the cathode lines of the LED were not soldered properly and were making contact by pressure they began to arc after a time when they oxided. This arcing effect cause the boost FET inside of the LED driver chip to short. This short then is interpreted by the software program to shut down some of the chip. I tried a work around which worked with one LED strip as really only 9 contacts are really being used on the 12 contact connector. Four contacts of each connector are connected to pin 32 of the LED driver chip and the positive side of the LED strip which is the positive voltage. Some of the Four contacts are connected through a 0 ohm resistor. The other 5 contact are connected to 5 negative lines individual of the 2 LED strips negative side and to the 5 different input pins to the LED driver chip. The unused circuit to the right is an identical LED driver circuit. I think the solution would be to supply 2 good LED strips with their own linear power supply with a rheostat to control the intensity and update the firmware program so it does not interact with the LED driver chip on the board.