LCD to LED conversions?

[OldLes]

My failure with the Sharp 42" set is somewhat dispiriting, and my pal drew my attention to a Utube video of a conversion to LED backlighting.
http://www.youtube.com/watch?v=LLIkS-cEuT0
Has anybody played about with this? It seems that CCFL, inverter board connections and simple inverter failures are commonplace, and the cost of a new inverter board for this Sharp, and the possible cost of any replacement CCFLs would be prohibitive. It also seems that CCFL tube failures are high probability.
So, what about LED conversions? I would guess about 500 LEDs would be needed, not sure how much, but it seems they are available in pre-created strips for some smaller sets. Done with care, it must be a foolproof repair surely. Would you have to tell the brain the previously existing inverter and CCFLs were all present and correct? If so, how?
Opinions please.
Les.

[OldLes]

I have a Toshiba 23" which needs an inverter transformer, so by way of experiment, I have just ordered a 5M strip of 300LEDs (cool white) for £8 which I will try to fit into the Toshiba just to see how it works. Not sure how I will control the output, or if I need to fool the TV to think its inverter is still OK and working. I may need help there, but will ask later if required.
Les.

[Keith]

Hi Les,

An interesting idea! But probably too costly. Good quality pure white LEDs are not cheap. You need pure white otherwise the colour reproduction of the LCD won't be very good. If you estimate 500 LEDs that will cost about £100 @ 20p each, obviously you could source cheaper if you didn't care too much about colour reproduction. you will then have to make them into strips and securely fix them. You could use the existing inverter PSU, and connect the LEDS in series groups.

If the TV will run OK with the inverter disconnected, I see no reason why it couldn't be done. But it would require a lot of experimentation. A 42" is probably a bit big, but I think it could be considered on smaller screens, if you have the time!.

I have just measured a screen and I think your 500 is about right. Looked on the old auction site and see you can get 5 meter rolls of white LEDs on a strip for less than £15, but I don't think they will be bright enough! Maybe worth a try, you have to start somewhere!

Will be interesting to see how you get on with this.

Good luck

Keith

[tv tony]

Interesting, but how do you propose to illuminate them, power supplies run pretty near their threshold as it is, the current consumption of all those leds wont be small.

[clark97]

Think I've got an Inverter + CCFL's + Connectors

[OldLes]

The idea of the 23" is to test the idea out. That way I will get some idea of the colour rendition, and could try various types of LED in the same set on a purely experimental basis. If it fails, I an £8 down and have 300 LEDs with which to play about. (They can always go in my junk box with about 500 neons [suitable for Grundig 5010, 5011 etc. touch control panels] and tons of other stuff collected over the years).

For the little Toshiba, I think that is a 12V supply to the inverter, and these cheapo LEDs require 12v at 2amp, maybe rather less than the inverter board.

Clark, If there was an easy way to get those bits off you, I would probably have them, but how on earth could they be posted without risk of loads of broken glass arriving?

The 42" can sit quietly for a while whilst I think about it. It was FOC from the amenity site, but would be worthy of a place in our living room. If I thought the LEDs would be suitable for that, I would certainly consider that as a solution, but obviously if the existing inverter / CCFLs can be sorted, that is the easiest solution.

[Keith]

Ah the old Gruntpigs, what a pain in the arse those touch controls were, changes channel when a fly walks across it. Not easy explaining that to the customers.

[Davy]

LOL Keith.

We had a Grunpig that kept changing channels by itself, the old lady hid under the stairs thinking it was a ghost.  The touch pad was laden in chip fat... all was revealed, her grandson came waltzing in with a bag of chips - nuff said!

Remember them GEC's too with their neon's, the good ol' days have gone!

Dave

[OldLes]

Hmm, I think we are getting off topic, but---    Actually, all my neons were for GEC, not Grundig, but they were essentially the same. In fact the 5011 and the 5012 (and others) used the same chipset as the GEC, even though the markings were different.  I bought a load of new GEC panels at a radio rally which kept me in chips for years, whilst the neons came from David down at Sendz. (I think he is still there, he supplied me with an audio chip for an LCD Phillips a couple of years ago).
Les.

[Davy]

Try to get back on topic here:

With LCDs there is ample filtering between the back light and the display, there are layers my mylar and silvered sheets to disperse the light usually mounted on a sheet of what I call mottled plastic to prevent casting shadows. 

Wouldn't LEDs require a different filter? I've never seen behind a LED display, doesn't CCFL's contain more UV light what little there is compared to LEDs, as you may know the LEDs are mounted round the edge.

Dave

[OldLes]

I decided at long last to start this trial conversion on the Toshiba LCD TV/DVD Model No. 22DV713B. Does anybody have a circuit for the main PSU/inverter board (or the complete set). The PSU/Inverter has No. DPS-65TP-3 marked so I assume that is its number.
What I had not bargained for with this is that set only has two side mounted CCFLs like a laptop, so I will try mounting them facing into the thick diffuser glass (plastic) as a start. If that is too dim, I will simply remove the glass and try perhaps six strips of LEDs.
OldLes.

[per]

Just for information. About 5 years ago I installed a number of LED in 3 defective 20 inch models (top & bottom). A transistor on the control line to activate a relay for the LEDs. (The 12v PSU was running in st.by.) All 3 TV is still running perfectly, now uses only 20W instead of 65W. The only broblem is: A little too dark picture, and in one of the models are the LEDs visible in small spots,(top & bottom) so I never tried it in a bigger TV.
per

[ProDave]

Are LED's really any more reliable?

I once repaired one of those little 7" digital picture frame sets with freeview built in.

I was appalled to find the LED's were just wired as a series string, so one LED failing was fatal. What actually seemed to happen was the first failed LED went short circuit, thus over running the rest (as it was constant voltage not constant current PSU) thus ensuring the whole lot failed very quickly.

I replaced all the LED's (re  soldered new ones onto the two strips) and had to re jig the PSU a bit as the replacements were lower current.

The set worked, but I sold it PDQ thinking the whole principle of it's operation was rubbish.

[OldLes]

With all the protection circuits in sets these days, I am quite certain a commercial LED set will have over current protection built in. Maybe your picture frame was just an early carp design.
No circuit anybody for the Toshiba main PSU/inverter board?  ( No. DPS-65TP-3)
Les.

[markc]

Interesting idea & should be possible,  but how will you control the brightness? The original inverter has a connection for brightness control!

Mark