backlight mod

[light0070702]

need help i have an lcd flat screen i'm a bit of a explorer so im looking to actually convert the ccfl's to led lights my question is as follows for any help i know the leds would need to be adjusted to to brightness settings in the tv itself is there a way to make a controller board to actually accommodate ever thing the tv adjust to make it adjust the leds

[stj]

Re: backlight mod

http://stores.ebay.com/lcd-led-parts...=p4634.c0.m322

[momaka]

Re: backlight mod

I have a feeling those LED backlight strips use cheap LEDs and so may not last very long. I bought long strips of LEDs for room lightning before, and many loose their brightness within half a year of daily use.

Reasonably priced as compared to CCFLs, though, so maybe worth it after all. CCFLs are a pain to replace, IMO.

[stj]

Re: backlight mod

no, they are good - i'm using a few of those kits.

as for the stuff you got,
i assume it's the flexable strips on 5m reels.
i'v looked at those and checked the resistors they use.
some are overdriven - probably including yours.
but a lot arent - specially the RGB ones.

there is nothing wrong with the led's they use - that's a myth.
the problem is some company's use the wrong resistors to get more lumens out of the strips.

[momaka]

Re: backlight mod

no, they are good - i'm using a few of those kits.

That's good. About how many hours of use have you gotten on them, though?

as for the stuff you got,
i assume it's the flexable strips on 5m reels.

Correct.
And yes, they are overdriven, indeed. Only 150 Ohm resistor in series with 3 LEDs. A single strip of 3-series LEDs draws a little over 15mA at 12V - too much IMO.

there is nothing wrong with the led's they use - that's a myth.
the problem is some company's use the wrong resistors to get more lumens out of the strips.

Right. But how do you know the LEDs in those strips you are using aren't overdriven either?

Those 5 mm strips I've used last anywhere between several months and a year (with approximately 8 hours/day use) before becomming noticeably dimmer.

The thing with LEDs is that you always have to make a 2 out of 3 choice: high brightness, long life, and low cost.

[stj]

Re: backlight mod

i'v used the led-backlight (edge-light) kits for about 4 months.
but i expect them to last because when i first got them, i powered them up outside the panel and checked the temp - they didnt get hot.

the sony ones in another thread are on an ally strip and clearly run hot - these dont.

about your strips,
did the led's die/strobe, or did the phosphor burn and make the output dim?
on the white led's i'v seen fail, the main problem was phosphor failure.

ah just read the last bit of your post.
yea, your strips are losing phosphor.
all white led's based on blue/IR+phosphor coat will suffer like that.
i prefer the RGB-blend type - they arent as pure, but there is no phosphor to fail.

[momaka]

Re: backlight mod

Is phosphor loss when the LEDs become brown or black? Because that's what most that I've seen do. Those 5 mm strips don't get hot at all either, which is why I am still skeptical about their quality. The other thing I have noticed is that cheap LEDs always appear to have an air bubble here or there trapped in the mold, whereas high quality LEDs don't and the mold looks very pure.
I guess time will tell. Nonetheless, I really do hope yours last. It'd be great to have an alternative to CCFLs.

[stj]

Re: backlight mod

phosphor starts very light yellow to golden,
as it ages it gets darker and the output drops.
some say it's caused by the heat on the die,
some say it's the UV.
whatever the cause, it happens eventually to all phosphor-based leds.
https://duckduckgo.com/?q=white+led+...t-wt&kv=1&kh=1

[mathog]

Re: backlight mod

no, they are good - i'm using a few of those kits.

That looks like it would go in nicely to replace a separate inverter. (Is there a standard pin out for those connections?)

Unfortunately most of the desktop display units I have repaired had an integral PS/inverter board, and the instructions for doing that are neither complete nor exactly in English. If you did some of these, did you hook up the dimmer part of the circuit? Did you post on this forum how you did yours? A picture is worth a thousand words. I have an old Viewsonic unit at home that just went to "3 seconds to black", and it would be a good candidate for this sort of fix.

It looks like what one must do is cut the power to the inverter side (in some manner that doesn't cause it to shut down the PS side) and patch this in. With no circuit diagram to work from it would take quite a bit of experience to recognize how to do that on an arbitrary PS/inverter board.

[cdicky]

Re: backlight mod

Have you thought of using an EL sheet?

Would using led's not require different diffusing layers than ccfl's. Otherwise you will just get bright white spots.

Also slightly off topic, anyone know a section on backlit keyboards (oem or mod).

And also, anyone ever done the opposite with lcd back light. I have an old TV that failed but the backlight works great. I wondered about converting it to a light box for crafting or similar?

[stj]

Re: backlight mod

light box? you could light a small area like a toilet or loft with a panel.
they are brighter than you think minus the lcd sheet.

defusers are fine going from ccfl to led.
and forget EL, it has low brightness and a VERY short lifespan.

[cdicky]

Re: backlight mod

light box? you could light a small area like a toilet or loft with a panel.
they are brighter than you think minus the lcd sheet.

defusers are fine going from ccfl to led.
and forget EL, it has low brightness and a VERY short lifespan.

LOL, not that sort of light box. But rather like this one
http://www.anythingdisplay.com/page/...oor_LightBoxes

Or the type you have on a table and use for doing pcb tracing, or similar work on

[stj]

Re: backlight mod

That looks like it would go in nicely to replace a separate inverter. (Is there a standard pin out for those connections?)

Unfortunately most of the desktop display units I have repaired had an integral PS/inverter board, and the instructions for doing that are neither complete nor exactly in English. If you did some of these, did you hook up the dimmer part of the circuit? Did you post on this forum how you did yours? A picture is worth a thousand words. I have an old Viewsonic unit at home that just went to "3 seconds to black", and it would be a good candidate for this sort of fix.

It looks like what one must do is cut the power to the inverter side (in some manner that doesn't cause it to shut down the PS side) and patch this in. With no circuit diagram to work from it would take quite a bit of experience to recognize how to do that on an arbitrary PS/inverter board.

missed this post - sorry.

all the ones i'v fitted have been to integrated psu+invertor type tv's
i said what i do in another thread, but i'll go over it again.

you remove the invertor chip so it wont send any fault codes,
you find the bl-on and dim signals and you find a 10-20v - maybe higher supply point.

what i actually do is more, i remove the fets, transformers,connectors etc.
so that i have a nice clear area on the original board.
then i stick the led driver on it with double-sided foam tape.
that way i keep the wires short and it looks tidy - no need to hunt some other place to stick the driver.

when the postman brings the next package i'll be doing a pair of LG's with combined invertor/psu's
i'll take lot's of foto's for everybody.

[stj]

Re: backlight mod

LOL, not that sort of light box. But rather like this one
http://www.anythingdisplay.com/page/...oor_LightBoxes

Or the type you have on a table and use for doing pcb tracing, or similar work on

i thought you meant the photographic/medical xray type
put a white screen on your tv/monitor and turn off the light in the room.
without the panel it will be about 20-30% brighter.