Bad backlights suspected on Sharp LC-C5255U LCD

[SurrealMustard]

I'm working on this Sharp 52" LCD (conventionally backlit; not LED) and it has what appears to be at least one dead backlight. It powers on briefly with a blank screen, then shuts off with a blinking green light. In the time that it is on, I can see a horizontal area that is dimmer than the rest, so I'm pretty sure that this is a bad backlight issue.

The trouble is, I can't find replacements anywhere for this model. Is there any way to find out what kind of backlight it needs without tearing the whole thing apart? If not, is there an easy way to bypass the system and rig it up to run with one less lamp?

[dskall]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

You could replace with a zener, but it would be easier to just replace the led

[budm]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

What is the LCD panel number? You may be able to get the CCFL or they may be EEFL from CCFLWAREHOUSE.

[dskall]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

My mistake. Missed that it wasn't led. Here's a video and example of bypassing a tube. Not for your set but may work.
https://www.youtube.com/watch?v=Dh01ZepjDp0

[budm]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

Bypassing in that Samsung or SONY only works if the lamps are driven by the Balancer circuit.
Similar to this one.
https://www.youtube.com/watch?v=oE6K4xBVweA

[SurrealMustard]

More details about this model; backlights replacement or bypass feasible?

I finally got the rear cover off and got a look at (as well as pictures of) the layout. There are two inverter boards on the right side and none on the left. The Runtka478wjzz inverter that this model uses appears to actually be for a Sharp panel (not just a Sharp-branded television). No sticker is obviously visible identifying the exact model of the panel, so I'm not sure how to find out what kind of lamps this thing needs (the sticker might be hidden under something though, so I'll try to keep an eye out).

If I'm reading the markings correctly, these inverters have number 2874025500 transformers on them.

Beside lamp replacement, the other question is, is there an easy way to bypass one of these in order to allow it to continue to operate without trying to run the defective backlight?

[dskall]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

It's possible one of the tubes came out of the socket and you would only have to reconnect

[SurrealMustard]

Socket reconnection q

It's possible one of the tubes came out of the socket and you would only have to reconnect

By re-seating the inverter board?

[Andrew F. Ali]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

If you are willing I could go through the process to convert your CCFL backlit TV to a LED backlit TV.....I am doing so currently with a LG 42in....I did it 5 times already but with 32in screens without callback.......

[attainteddragon]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

andrew, i think a lot of us would like to see a thread on this. would be very handy to know how to do this conversion.

[SurrealMustard]

Cool idea, but is the transfomer bypass feasible on this one?

That sounds very interesting and while I would love to see what that process looks like, this particular Sharp isn't mine and I'm on a bit of a time cruch to get it sorted, so I was hoping that somebody had a suggestion for the "easy fix," bypassing the transformer for the downed lamp. Any ideas for how to do it on this particular inverter?

[dick_barton]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

If it's a tube fault then they appear to be available from
http://hdtvparts.net/products/3169-l...2d85u-lc-.aspx

[culcuhain]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

Also one of those inverters might have failed. You might be able to just find the wrong inverter, replace it and be good. I did this on a 32" I had. $7 for the part and tv was back in business.

[Andrew F. Ali]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

andrew, i think a lot of us would like to see a thread on this. would be very handy to know how to do this conversion.

I'll format a document and post it for review, soon.

[attainteddragon]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

I'll format a document and post it for review, soon.

awesome, looking forward to it.

[attainteddragon]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

pic of the inverter board please.

have you checked the output windings on the transformers yet?

[SurrealMustard]

I'd like to; how?

pic of the inverter board please.

have you checked the output windings on the transformers yet?

I haven't yet. Any advice on how to do so?

[attainteddragon]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

measure the resistance on the output pins of each transformer.
i havn't had to look at this type, but looks like one transformer per ccfl.

power off of course.

the one that relates to your non illuminated ccfl may of failed.
if it has, it will have a noticeable difference of resistance compared to the others on the inverter board.
if so, you can replace it and have the tv fully functioning without any bypassing needed.

[SurrealMustard]

Infinite resistance!

measure the resistance on the output pins of each transformer.
i havn't had to look at this type, but looks like one transformer per ccfl.

power off of course.

the one that relates to your non illuminated ccfl may of failed.
if it has, it will have a noticeable difference of resistance compared to the others on the inverter board.
if so, you can replace it and have the tv fully functioning without any bypassing needed.

I'm getting infinite resistance on all of the transformers when testing those output pins with the multimeter. It's not an auto-ranging meter, but I've gone to each transformer and ratcheted through all of the different resistance testing options to no avail. Am I doing something wrong?

[dick_barton]

Re: Bad backlights suspected on Sharp LC-C5255U LCD

Pinout of transformer