Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

[PeteTait]

I Acquired a 42" LCD with the Symptoms of No Picture No Back light. But there is Audio. I have been reading a lot of different post but i doing thing anyone as really answered the question. What part could it be. I am Novice to a lot of the talk and have been researching and trying to find all the different things and test points people have been mentioning.

So with the TV i have. i have been able to test the voltage to the Inverter Board and i Do have 24volts. I also found the (on/off) test point and read 2.7volts . then the (I-Pim) 2.1volts . I also found the DIM in and out by a ribbon from the T-con board. I Got no reading on either.

Recap All check with tv powered on.
24volts at inverter board.
(on/off) 2.7volts
(I-Pim) 2.1 volts

DIM in- 0 volts
DIM out- 0 Volts.

What else should i check or need to check. Please help so i know what to do to fix.

[multimeter]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

we need to know if the mainboard is working 1st.

do you see a image on the screen if you shine a strong light at the screen?,i normally press the menu button on the remote,as this will give you a stronger image and a better chance of seeing something.

if image is there ,you will have an inverter fault.

possible causes.

bad caps.

bad ccfl tubes.

blown inverter fuse (can be no other fault).

psu voltage to inverter missing or low.

shorted transformer ,normally secondary shorted on inverter.

[PeteTait]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

Thank you for the response.

So i just did the Flash light test and Yes after i press the Menu button on the TV, i do see the Menu. But it is only Visible with flash up the screen.

[multimeter]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

good,you have an inverter fault,start by checking the fuse,and the voltage on it.

black probe cold ground (chassis)

red probe both ends of fuse,you should see around 24v on BOTH ends of the fuse on the inverter.

[PeteTait]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

I attached a Photo, Just for Clarification. I believe the fuse would be Labeled F1 on the board. Correct? Hopefully you can see it

[multimeter]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

I attached a Photo, Just for Clarification. I believe the fuse would be Labeled F1 on the board. Correct? Hopefully you can see it

yep thats the one,id expect to see 24v ish,both ends of that fuse

[PeteTait]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

Well well well, I have 24v on one side but not the other!

[multimeter]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

Well well well, I have 24v on one side but not the other!

ok,now power the tv off,unplug from wall.

do a resistance test accross that open fuse,you should see hundreds of ohms,a few ohms will indicate a short on the inverter board.

if you find this ,then we know the board isnt shorted

for a go no go test,just bridge the fuse with a blob of solder and retest power on ,tv on

,only after the resistance test proves negative

[PeteTait]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

I am Measuring .493 M Ohms so that would be like 493000 ohms.

[multimeter]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

I am Measuring .493 M Ohms so that would be like 493000 ohms.

thats good,no shorts on the inverter board.next step

put a temp bridge of solder accross the fuse

power up tv ,you should have a back light

[PeteTait]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

Alright, Well i put a small jumper over the fuse and she fired up! So i can just leave it like that right!! Kidding I will order a new fuse.

[vinceroger69]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

dont you just wish that all backlight repairs was this easy and glad it was a straight forward repair for you and another tv saved from the recyling centre.

[multimeter]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

Alright, Well i put a small jumper over the fuse and she fired up! So i can just leave it like that right!! Kidding I will order a new fuse.

well done !,next step is a new fuse,the reason why it blew,is because of bad design,its rated to close to the actual current draw.

what you need to do is remove that fuse now,put your meter and the correct probe on amp setting (10a),make sure your brightness is set to max on the tv.

measure across the fuse,with power on,you will find the backlight will come on ,the ampmeter will act as a "fuse ,this will tell you the current draw in amps

pick a fuse with same voltage but a higher amp,yours is most likley about .75 amps?,a 1 or 2 amp should be fine depending on the amp draw.

put new fuse in,reset brightness,and your done.

[PeteTait]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

I found a Direct Replacement for the one that is junk. any suggestions on a site that i might find a 1amp or 2amp?

http://www.encompassparts.com/item/8...Fuse_0.75A_Smd

[multimeter]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

^ try cpc,farnell ,rs components,you could also use a pico fuse of the correct ratings

[multimeter]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

or ebay in your area

for instance http://www.ebay.co.uk/itm/MC06CF-002...item53fab6393b

[ptepe]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

I have the exact same problem though my screen first comes on then goes off after a second or two. Did test on inverter board and found that one of the two 8a/160 volt fuse is open. I have 24 volts measured at both white fuses but one doesn't read 24 volts on other end. When I close the blown fuse with an alligator clip, it shuts down the 24 volts completely as their seems to be a short. Does this tell me that the inverter board has a short? I checked the 4 caps on that side of the fuse and they're fine. Is it possible that there's a short in one or more of the transformers on the inverter? Any help would be fully appreciated. I want to make sure the inverter board sounds like the problem before i dump money into it.

[66bugman]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

i am having the same no picture issue when i use the flashlight i see the logo but the fuses both have 24v on both side what would be my next step

[MisterD]

Re: Philips 42PFL3704D/F7 No pic/No Backlight, w/Audio

Ptepe and 66bugman, I suggest that you both start your own thread with model number of tv and pictures of all the boards, then you will get a better response. Most people will not even see what you posted here.