Repairing LCD panel, fuses bad i think?

[dirtyb15]

Hi all, I just opened up a hdtv lcd monitor, that was black, but could see picture in the light if i looked hard. Anyways, thought it was the backlight but to my surpise there are 2 one on top, and one on bottom. (maybe this is common i dont know.) but i thought it was odd that both would go. So then i looked at the inverter. Looks like there are two surface mount fuses i think? Labled F1 and F2, so makes sense that they are fuses. They both measure open, so id like to try and replace them and see if it happens again. ONly letters on them are FN. Can anyone tell me if these are indeed fuses, and if they are, any guesses as to what ampreage they are?

 

[Sceadwian]

The more important question to ask is what blew the fuse in the first place. Aside from finding some markings on the fuses without schematics to work from you need to determine what the backlight element actually is and it's voltage and current requirements to determine the amp rateing of the fuse. If you think it's just the fuses themselves that's wrong, you can always just short them out and see if it was just a fluke power surge. But if it wasn't there's a good chance it'll go up in smoke. Then again if all else fails what's there to lose?

 

[dirtyb15]

Well, I got it for free, and dont know the history. B/C i dont know why they blew i dont want to short it . The power adapter cannot be found for it, so im wondering if maybe someone hit it with more than 12 volts or something like that, but it does seem odd that only the inverter board is not working. I am guessing it was just a surge though, as both fuses are blown. (its kind of like two separate circuits on one board, one for each backlight). Ill see if i can find any specs on these backlights. Thanks!

 

[Nigel Goodwin]

Usually they are quite a large number of inverters, one for each tube - presumably they are clustered in groups on two panels on your set?. If any one of the inverters is faulty, the entire lot will shut down.

 

[dirtyb15]

Correct nigel, there are 2 groups. I was bored last night, so i figured i wired in a small fuse on top of each of the two fuses, and to my surpise i had light again. (and no smoke . ) I am sure the fuse rating is wrong, so now if i could only figure out what was in there.
Thanks for the input guys.

 

[Sceadwian]

If it's working again then your sollution is easy. Instead of a fuse use a meter on current measure mode and use that as the fuse, monitor it for a while to determine the current. It really should be constant, value your fuse appropriatly.