Philips 32PFL6606T 32" LED no back light

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

ill try and get a better picture of the board tonight, my cameras not that great, because the picture of the diodes i tested isnt that clear to see the tracks and how its connected

[multimeter]

Re: Philips 32PFL6606T 32" LED no back light

full strip down, but if there is 4 sets of LEDs and only 2 sets are getting the correct 150V surely this means the fault lays on A3 and A4 supply somewhere because there not getting the full 150v there only getting 72v?

im inclined to think that a1 a2 a3 a4 are paired and 2 sets ie a1 & a2 are running off one transformer and a3 & a4 are running off another transformer,have you tested the voltage with the plugs removed from the board,and tested at the pcb itself? if the voltage comes up at around 150v on the plug footprints then it could be the led network has shorted,but then again an led diode normally dosent go short circuit they go open,its worth a shot before stripping down to the panel to get to the leds,im facing the same problem with a sharp lc-46le700e where i have voltage at the led plugs but backlights arnt turning on with 2 flashing leds on the main board ??,oh hum the saga continues

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

I'll try that when I get home, the transformer that feeds them both has one primary and 2 secondary

[tom66]

Re: Philips 32PFL6606T 32" LED no back light

If you've got voltage to the LEDs you probably have an open LED. You need to test each individually which can be done with a meter which puts out more than 3.5V on diode test. Some do - mine does - but not all do. Check with a white LED first. As an alternative you can use a CR2032 coin cell and tape some wires to it; it will make the LEDs light up individually if you power them. The LED which doesn't light up needs replacing but it could just be shorted with minimal affect on the picture, if the LED array is large enough and the diffuser is good. You must test both ways as LEDs conduct only one way and it may not be obvious which way is positive.

If you have a higher voltage, current limited supply, you can light up a group of LEDs all at once to speed up testing.

Thinking about it a 16:9 TV will have more voltage on the bottom edge LEDs than the side LEDs as there are less on the side. In fact 150V vs. 72V is about 16:9 ratio (should be 84V on other LEDs, but might be limited by the open circuit in one chain, or the brightness might be different on the sides of the panel.)

This is just like finding a bad bulb in a set of Xmas lights.

[multimeter]

Re: Philips 32PFL6606T 32" LED no back light

I'll try that when I get home, the transformer that feeds them both has one primary and 2 secondary

the secondarys are more likely to fail than the primarys,a ring tester would be good to test them if you have one,if you dont it would be a case of testing both the secondarys and see if they are the same within reasonable tolerance

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

Think I checked them and they were the same, but that was in circuit so could be false reading, ill check voltages again with the plug out, and do what tom said if I'm getting the voltage, if not ill take transformer out and test it

[tom66]

Re: Philips 32PFL6606T 32" LED no back light

the secondarys are more likely to fail than the primarys,a ring tester would be good to test them if you have one,if you dont it would be a case of testing both the secondarys and see if they are the same within reasonable tolerance

That might not work for SMPS transformers, different # of turns per winding. You have a voltage - that should be enough to make the LEDs glow - but they don't from what I understand.

[multimeter]

Re: Philips 32PFL6606T 32" LED no back light

That might not work for SMPS transformers, different # of turns per winding. You have a voltage - that should be enough to make the LEDs glow - but they don't from what I understand.

i mean the transformers that supply the voltage to the leds,not the smps transformer,thats a point im wondering if the tv has edge lit backlight or compete array of leds all over the screen?

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

I'm not sure on that 1, but ill let you know if I have 2 strip it down

[tom66]

Re: Philips 32PFL6606T 32" LED no back light

i mean the transformers that supply the voltage to the leds,not the smps transformer,thats a point im wondering if the tv has edge lit backlight or compete array of leds all over the screen?

Those are just regular SMPS transformers. Measuring the resistance only works for Royer oscillator inverters, which balance current through the CCFLs using the resistance.

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

just checked voltage.... 150v going out to both A1 and A4 , so its souning like a LEDs gone, so gonna strip it down in abit, ill post some pics when ive got it to pieces, problem is the service manual only shows so much so i figure im on my own, just have to be gentle with the screen when i take it off

[multimeter]

Re: Philips 32PFL6606T 32" LED no back light

just checked voltage.... 150v going out to both A1 and A4 , so its souning like a LEDs gone, so gonna strip it down in abit, ill post some pics when ive got it to pieces, problem is the service manual only shows so much so i figure im on my own, just have to be gentle with the screen when i take it off

before you do ,is there a lead coming from the power supply going to the t con board?and i mean separate from the lvds ribbon cable,check to see if you have the correct voltage,if not then this supply may come from the main board,and could be throwing you a little,most led tvs get there switch on supply from the main board

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

no there is one going to main board then ribbon cables from the main board going to t con (X 2) and other one on power board going to the LED panel

[multimeter]

Re: Philips 32PFL6606T 32" LED no back light

no there is one going to main board then ribbon cables from the main board going to t con (X 2) and other one on power board going to the LED panel

and are you getting any voltage going to the t con?

[multimeter]

Re: Philips 32PFL6606T 32" LED no back light

Those are just regular SMPS transformers. Measuring the resistance only works for Royer oscillator inverters, which balance current through the CCFLs using the resistance.

sorry tom yeah your right,just looked at the pic again

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

the picture is fine, i can see the menu's and setup screens coming on, its just the back light
all voltages are correct, you went through that with me before

[multimeter]

Re: Philips 32PFL6606T 32" LED no back light

right you are ,time to test the leds then,make sure when you take out the diffuser sheets you dont get any dust or hairs inbetween on re-assembly ,if you fix the dud led or led rail,it will show through when the pic comes up,i usually use a can of air duster

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

would it be a wise move to wear some powder free latex glove? so i dont get finger prints on anything?

[tom66]

Re: Philips 32PFL6606T 32" LED no back light

would it be a wise move to wear some powder free latex glove? so i dont get finger prints on anything?

As long as you don't touch the inside of the LCD, you should be fine - but it doesn't hurt to take precautions.

[shepp]

Re: Philips 32PFL6606T 32" LED no back light

oooo my god what have i done...

ill post some pics after ive eaten, but the LEDs are round the edges top and bottom, i havent managed to take the suspected strip off yet....my diners nearly ready

this is scary stuff....i really dont wanna damage the screen, but its out and safe with all the glare etc sheets, god knows how im gonna solder the new LED in...thats if i can get one(if i can find the one thats gone)