Sceptre 48" TV Faint Picture

I have a sceptre 48" TV ... Pin: E485BV-FMQR8BK AV93BA S/N E23B485CB0239

The picture is very faint I can barely see it. Is the backlight bad and needs to be replaced? If so where can I get the part?

Thanks for reading my post.

 

Search online for parts for your TV. Even if new parts are not available there are many who part out old TV's but a quick search turned up parts for your model.

" Is the backlight bad and needs to be replaced?"
We cant see or test your TV so you'll have to diagnose to find out what's bad. If you have dark areas on the screen then maybe a LED or section of them is out. If everything is dim you'll have to find out if the LED's are illuminating at all. If not you may have to check their power supply.

 

I'm pretty sure the backlight is what needs to be replaced ... the problem is I haven't been able to find a replacement... I;ve looked on ebay, but so far no luck. If I can't find the strips I was hoping I could find the leds that fit and test each one until I find the bad ones. I saw a video of a guy working on the tv I have and he found one bad leds which cause to whole screen to go dim to the point you could barely see it. That is what is going on with my. So my problem is finding a replacement.
If anyone knows where I can get them please post.
That for a sceptre E485BV-FMQR.
Thanks for reading my post.

 

Get the part number off the light strip. Maybe searching for that will yield better results than searching by the TV's model number.

 

I have repaired strips. Typically you can see the burned LED's.

Left two links.
Shop Jimmy is the "go to" parts place for LCD TV's.
ShopJimmy custom link
Sceptre parts

 

I contacted shopjimmy a couple of days ago he told me he didn't have the part I need.
When I take the TV apart I will get those numbers. I saw a video where the guy replaced the led instead of the strip. Turned out that one bad led was causing the whole problem. If I can't find the strip I hoping I can find the leds that will work in that set.

 

I love taking flat screens apart. I find it fascinating how they are made. Especially, the low end simple models. I love the tricks they use to distribute the light evenly from a couple strips of LED's. There is an amazing amount of technology and engineering at a ridiculously low price.

 

My neighbor has a big LCD screen over a pellet stove insert. There are bulls eyes at every working LED. I had told him when he installed the pellet stove that he would cook his screen.

It's still going but very annoying. Easy to see the dead LED's.

 

I plan to take the TV apart some time this week. If you like I can post photos of the process.

 

Wellsir ... I found this excellent how to video showing step by step on how to take a Sceptre 50" TV apart and how to check the backlights. Now I see toward the end after he installed a replacement LED he turn the power on, but when he was checking for the bad LED I wasn't sure if he had power on or the LED held their own power. I guess they must when he checked the single LED, so the strip should read 38V.
I'm hoping I can find the strip that will work, because according to the video those LED's are hard to come by.

Also from watching the video I found I have to order some suction cups to remove the screen and a heat gun if I have to and can find a LED. I will have to wait until the parts I order get to me next week sometime.

The manufacture really put up blocks to discourage anyone from fixing it instead of getting a new one.

Thanks for reading my post.

 

It's not that they are trying to make it hard to work on.
They've spent a lot of time and money in building a TV fast and cheap with no thoughts of servicing.

 

Okay ... I finally got the TV disassemble. However I don't know how to test the strips. The guy in the video I posted had something a little different for the backlight. How do I test them with a multimeter? Do the attached photo show what kind of strip I need to find? One shot isn't that clear ... if you can't make it out I will take another picture.

 

I found something on ebay and amazon ... it has the same number ... will they work?

backlight on ebay

 

For some reason I could not put the amazon link in with my last post so here it is.

Amazon backlights

 

Can anyone tell me from the photos posted where the test points are on the strips. How do I test it with a multimeter. Do I set it to volts, and I'm guessing I don't have to power the tv to test them. In the video link I posted the test points are different than the strips I have, so I don't know for sure.

 

Here is a more clear picture ... do I need to remove the covers to get to the test points? Since there are 12 LED per strip with 3v per LED I should get a 36V reading with the multimeter set at the diode setting?

 

I added random lines to the pic. They don't indicated polarity.
It looks like the orange is the largest foil area and is probably used as the heat sink.

Set you meter to the diode setting.
Check at the connector in the red circle.
Check in one directing and then the other direction.
Check them all to see which ones match.

Typically defective LEDs are black or have a black spot.
Not sure if those lens can be removed.

To check each LED you'd need to scratch thru the paint.
I put black dots where you'd need to check.
I use probes with needle points that easily puncture the paint.

These are Fieldpiece leads that connect to your existing probes.... fieldpiece probes.
They have sharp points under those black boots.
Similar on amazon..... fluke sharp point extensions

 

Wellsir ... I took a 9v battery and selected 3 led to put my probes on the + and - end to see which would light and which would not. I found 5 bad leds. Now that I know where they are I can replace the strips with the bad ones.

I'm going with the ones they are selling at amazon ... price is more reasonable

.

 

Hummm ... the strips that amazon and ebay are selling have 5 leds per strip while I have 6 leds per strip ... the part number is the same, but I am wondering if they will work.

 

Were you able to measure the voltage on any of the strips when the TV was running ?
If it's the same part number.... I would think they should work.

Some LCD driver supplies shut down if it detects any defective LED's
That means you might not be able to measure the voltage to a strip.
I'd want to know the operating voltage of one strip to see if the new one is the same.

 

I didn't get any voltage reading on the strips when the tv was on. I asked the seller on Ebay about it hopefully he will know for sure. I would think with each led needing 3v it would be 18v total. With the 5 is should be 15v, What do you think?

 

I think you are assuming that groups of LEDs are wired in series. More likely they are paralleled, which requires only 1 common voltage; such as 5 Volts.

 

The driver that supplies them power may be a current limited rather than a voltage regulator.

It looks like those may be series strings. You can determine that with your meter set to Rx1 not diode scale.

 

The leds are in series ... I'm trying to make sure the replacement strips will work with one less led actually two less if I count the two strips to be replaced.

 

I did some emails to the seller at ebay to determine if the strip would work, I sent photos of all the numbers on the strip and he told me what he sells will not work in my TV and there are no replacements for it.

I order the set of strips from amazon so I have to see if the led will work in my set if I replace the the 5 bad leds.

 

Wellsir ... I went with these strips from Amazon it was far more economical to get a set rather than one strip in case I find more bad leds, the strips are shorter of course than the original so I plan to replace each bad led, it looks like the leds are the same. What do you think? I just need to make sure the polarity is right. The guy in the video I posted showed how to remove the bad led and replace it with a good one. That was the only numbers on the replacement strip.

 

The easiest way to determine the polarity of any diode without damaging it is to use a watch battery. In post #16 the boards are market with polarity.

 

Wellsir ... I am having a problem getting the new led out of the strip. I had no problem removing the bad leds with a heat gun, but I tried with the soldering iron and the heat gun they will not come off. Any ideas how to remove the led. It should come off with the heat applied ... what am I doing wrong?

 

It could be how it was manufactured. Some components are glued in place. This is sometimes done with larger components that can vibrate out of position as the board is moved on the conveyors before the reflow oven that melts the solder. Most smaller components can stay in position with just the stickiness of the solder paste.

 

Even if it were glued on wouldn't the heat soften the glue so the led could be removed? There must be a way to remove those leds ...does anyone have a clue?

 

If it is glue that is holding them in do you think nail polish remover would loosen it without damaging the led?

 

I don't know if the component you are working on is glued, but it is a possibility.

Glue is used to hold the part securely in place through soldering. So, the glue is designed to NOT break down at high temperature. Also, many things are not designed to be disassembled. Even in a factory with all the right tools there are some errors that are not reworkable and cause boards to be scrapped.

If there is glue, it is protected on the top and bottom and baked on. Any solvent you get to wick under the component can only contact the very edge of the glue and can't reach the glue in the center. So, it may take a lot of washing to work.

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Surface mount repair without the right tools can be quite tough. If you try hotter temps or heat for too long a time you can damage components. The temperature to flow the solder is above what can damage many components like white LED's. During manufacturing they get away with it by carefully controlling the temperatures and time and rapidly cool before the heat can soak into the component. So, working at home you have to be mindful to not just apply more heat until it comes off, or sit there roasting it for 30+ seconds while you fiddle with it. Sometimes you have to hit it hard/hot for a few seconds then cool the part. Of course thermal cycling isn't good for the components either. Luckily you've got extras so you can perfect your technique and once you've got the process dialed in you can harvest the LED needed for your repair.