Seiki SE50FY28 LED TV, no backlite

[dogdad]

I've made great progress in learning about and repairing several 'homeless' LCD TV's, and now wrestling with a Seiki SE50FY28 LED TV. Very little information on it, and no repair info at all.

In a dark room, there is a very faint image, and when I pulled the screen panels apart a little and did the flashlite test I can see it more clearly. That tells me the backlites aren't being driven. But I don't know which of the wire bundles are for the LED drivers, or for that matter which board is driving them to test anything.

I'm reluctant to pull the screen(s) apart any further either to reach the LEDs. After removing a zillion screws on the trim, I did see the outer-most panel with the image on it, and behind it is the translucent panel where I 'suspect' the LEDs live. However, before going any deeper, I'd feel more comfortable knowing I'm heading in the right direction before destroying something.

So, two related questions...
1) Which board drives the LED's?
2) What voltages should I find (and on which connectors) for the LED's to determine if it's a board failure or a bad LED (or string)?

Thanks in advance!
Ron

[dick_barton]

Re: Seiki SE50FY28 LED TV, no backlite

Hello Ron,
If you post pictures of the circuit boards (back of set) and how they are connected then members will be able to tell you what each one does.

[dogdad]

Re: Seiki SE50FY28 LED TV, no backlite

Sure thing, should have done that in the first post!

Taken with a camera phone, so the quality is less than stunning.

[dick_barton]

Re: Seiki SE50FY28 LED TV, no backlite

Here we go.
Can you give a closeup picture of the Led power cables on the power supply so we can see the legend alongside the connectors.

[flocko]

Re: Seiki SE50FY28 LED TV, no backlite

the five plugs with the red and white cables are the LED string feeds (right side of power board ) so check these for DCv

[dogdad]

Re: Seiki SE50FY28 LED TV, no backlite

By you mentioned the LED wires, that confirms what I had guessed as well.

Ok... Photo 0962 is where red/white wires are going into the chassis at the bottom. And 0960 is the close-up as they came off the board.

Thanks so far!

[dick_barton]

Re: Seiki SE50FY28 LED TV, no backlite

Can you measure the voltages on CON11,12,13,14 & 15 and post them here.
Image courtesy of Shopjimmy

[dogdad]

Re: Seiki SE50FY28 LED TV, no backlite

C11 28.2vdc and steady
C12 16-23vdc and 'jumpy'
C13 25.6vdc and steady
C14 33vdc and fairly steady
C15 20.3 and steady

If they're supposed to be fairly steady and similar, kinda sounds like the board, eh? What should the voltage be?

Wife just noticed that the display (or what little can be seen, it's so dark) also flickers, probably in tune with C12

Thanks!

[flocko]

Re: Seiki SE50FY28 LED TV, no backlite

these I think will be wired in series on the back of the board , but you would need to check? so it looks like one string is down, have a look to see if the sockets are looped on the back?

[dick_barton]

Re: Seiki SE50FY28 LED TV, no backlite

This may help you:
https://www.youtube.com/watch?v=UxR8-xztdGs

[budm]

Re: Seiki SE50FY28 LED TV, no backlite

The LEDs are connected as one big string, the L+ (CON11) is the Anode feeding pin, so what do you get on that L+ pin?

Pictures provided by shopjimmy.

[flocko]

Re: Seiki SE50FY28 LED TV, no backlite

So you should be able to use 9v batteries in series to test each line would think 3X9v=27v should get them to work

[budm]

Re: Seiki SE50FY28 LED TV, no backlite

So you should be able to use 9v batteries in series to test each line would think 3X9v=27v should get them to work

fOR 50" TV with one big string of LEDs, the Boosted Voltage feeding the string will be A LOT higher than 29V feeding that big strings of LEDs, he needs to leave the meter on the L+ then turn the TV on to see how high it jumps up to before settling to 29V range.

[budm]

Re: Seiki SE50FY28 LED TV, no backlite

Same power supply-LED board used in these threads:
https://www.badcaps.net/forum/search...archid=6197586

[dick_barton]

Re: Seiki SE50FY28 LED TV, no backlite

Your correct once again budm. From the links you provided it looks like 5 led strips connected in series at the power supply end and each strip at approximately 30V dc driven so overall the power supply should be providing approximately 150V open circuit voltage.

[budm]

Re: Seiki SE50FY28 LED TV, no backlite

Those typical LG LEDs that failed very often.
http://www.shopjimmy.com/seiki/se50fy10

At this point we need to verify that the boost converter circuit is working or not first by leaving the meter probe on L+ pin and turn on the TV and watch the DCV.

[flocko]

Re: Seiki SE50FY28 LED TV, no backlite

Did i not say to test each string (line) going to the screen 5x27v or is it me going mad. I thought Ron was asking if he could to test the LEDs without striping the set? this is the way i would do it. You can buy 10 X9v batteries for £7.00 on ebay find a cheaper 9v> 90v supply. (see photos)

[ReeceyBurger123]

Re: Seiki SE50FY28 LED TV, no backlite

Watch my video in how to repair the strips, easier and cheaper than replacing them all:

https://m.youtube.com/watch?v=RxwdC7V5Ue0

[budm]

Re: Seiki SE50FY28 LED TV, no backlite

14 LEDs per strip as shown in the picture, so 14 LEDs x 3V = 42V, I would use constant current source otherwise if you have shorted LEDs (I ran to bad strip with 5 shorted LEDs before) and you just apply the power source without current limiting then you can damage good LEDs since the to total Vf will no longer be at 42V, that is one draw back of using straight power source with no current limiter when you may have shorted LEDs on the strip, the strip will still light up with shorted out LEDs.

[flocko]

Re: Seiki SE50FY28 LED TV, no backlite

Budm That is why i said three 9volt =27v my thoughts were from what 50"sets i have worked on.(9 or 10 LEDs per strip) And as we dont know the number of LEDs on each strip in this set, it has yet to be taken apart,he just wanted to see if there was a way to test the LEDs before doing so? I do not have a clue as to were the photo came from that was posted showing LED strips on the gutted set.Anyway you seem to have it covered so I will leave this one to you as he is on your side of the pond and on your time line Regards Flocko