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Marine monitor with backlight problem

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2PAC Mafia

Member
Hi guys,

I have a marine monitor with backlight problem. The unit uses 17" LED driver P/N: DRV-LTC83x2, it´s based on IC LTC3783EFE as controller. I´ve seen the board is sending power for a moment to the LED strip and then is stopping. I saw PWM at gates for a moment too. I guess the LED strip has some problem or interruption and then the board is protecting itself.

I put direct voltage at LED strip connector and it´s not consuming anything, are you agree with me that the problem is at the LED unit itself?
 

dr pepper

Well-Known Member
Most Helpful Member
The bond wire within an Led is a known failure mode, flicker and intermittent operation before failure also happens.
I'd expect several chains of leds in the monitor backplane, the driver might well shut down if it notices too low a current, however when you powered the backlight some of the Leds would still light if this were the case.
You might be able to work out if all the Leds are in series by looking at the voltage rating on the caps that have the Led supply voltage on them.
 

2PAC Mafia

Member
Thanks dr pepper. Finally I got access to the LED strip. I had to break the crystal of the screen, no other way to access as it´s in a metal frame all together with glue...

The driver is not the one used in the LCD itself, it uses one external so the LED bar I guess is also different. I have 66 LED in 6 group of 11 in parallel and when I give 3V individually to all of them they work. The capacitors at the output of the driver are 2 of 22uF 50V in parallel, so it has sense that 40V is the correct output.

Now the strange thing, when I give 40V power only some strip of 11 is lighting, only sometimes!!! If I measure with continuity to see connection to the connector and to the LED´s I can see how they are in parallel of 11 units so I don´t understand this behavieur. Some pictures attached.
 

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dr pepper

Well-Known Member
Most Helpful Member
Sounds like a case of dead bond wires, however that would mean some wouldnt work when powered individually, maybe a bad connection to the board or an open trace then.
Looks acedemic now though, with the glass broken doesnt look as though it'll work again, or do you have some idea of getting it back togther again?
Those led's are probably good quality ones wih matched intensity and colour temp.
 

2PAC Mafia

Member
Yes, for sure there are problems, bad contacts. About the crystal I can put a new one and the LCD I can buy too. I can repair those parts but now the problem is this LED bar without any reference on it... These displays are very expensive, they can be more than 5.000$, this is why I went so deep in the repair.
 

dr pepper

Well-Known Member
Most Helpful Member
I'm surprised you can get the parts for it, I spose at that money some will repair them.
Maybe if you powered a strip then flexed it around with a 'driver and see if you can find an open in the board, on a board that isnt lighting if you set your power supply to current limit you could short out each led with a pair of bird beaks, when you get to the bad one the rest should light, assuming no more than one is bad.
If you replace any leds, colour temp match might ne an issue, maybe not so bad for just one or two.
 

ci139

Active Member
about that
stuff
F;x if your warranty was expired such may be considered -- while my family member had problems with it's brand new NoKiA ...
  • first they did some "dust wipe off" (at the local representative's service) -- which didn't affect the issue of the battery loosing charge and not charging properly
  • the 2-nd time they tested everything and made complete software update -- which didn't affect the issue as above
  • the 3-rd time they sent this thing back to factory and got the entire inhold (content) replaced -- that did the magic
all this took several month . . .

what i'm trying to say here , is that there is cause for the LED backlight malfunction (no matter the reasons) -- either you keep replacing them one after another or you let the manufacturer deal with it's #### . . . or choose a more reliable brand -- there's no point of attempting to fill a production quality holes in person at your own budget ...
 
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