Replaced Inverter and CCFL still no backlight

[wang890]

i got a hp 8530p that i found in the trash from another company. missing many components however i got them all on ebay and craigslist.

the only thing left to repair is the CCFL. same usual symptom. shine flashlight on screen can see the lcd is working.

i replaced the inverter and same thing. couple days ago received ccfl from ebay and yesterday spent 1 hour taking the lcd apart, once got to the old ccfl and i noticed one corner is shattered. that explains why there is a dent on that corner on the laptop aluminum case. i soldered it carefully to the new ccfl, keeping in mind no more than 4 seconds touching that with soldering iron. i didn't test and put everything back then tested and no backlight.

the funny thing is on the inverter, there is a ribbon connected to the LED on top of the screen which is used for lighting the keyboard, where normally it's a camera but my one doens't have camera. This LED works for both inverter.

i have a multimeter goes to 1000vdc and 750vAC. i tested the inverter entrance area and got 16vDC. then no voltage at all on the CCFL connector side. i read those are over 1000v so no meter works for it.

so if the inverter works all the way to the ribbon to the LED what could possibly be wrong that the ccfl is not lighting? pretty sure i didn't damage the new lamp but i couldn't be certain.

i want to desolder the ccfl and maybe touch the wires while it's powered on to see if it can shock me with 1000v then i know it's working. or maybe touch that on some metal to see if it sparks. that's the only way i can think of.

i can upload some pictures but i think my description is decent.

i am thinking it could be the main harness to the inverter, it has many wires on it. could one wire be bad that causes the LED to work but not CCFL?

i am also thinking maybe i can drill a bunch of holes and stick in some LED and making this LED. shouldn't be that hard yeah? i saw one guy did it on google search. i already see all the filter layers and even the glass panel underneath the LCD which is used to transmit the light across. totally understand how everything works.

maybe i should get the ccfl which is soldered already. but it shouldn't be hard to find out if the inverter is outputting voltage.

any ideas?

thank you so much.

here is good picture for inverter

http://www.laptop-spares-online.co.u...book_3533.html

[highpulse]

Re: Replaced Inverter and CCFL still no backlight

Have you checked values from KB controller ? KB controller enables the Inverter . if the controller of the inverter doesn't receive the Enable signal , inverter will not turn on , my advise to double cheek this , is to , unmoved the Enable cable fmor the inverter and inject with a power source 3.30 volts on it , to see if the inverter will turn on . if it will work , can be multiple things , cheek traces near KBC and near the lads connector , also make a continuity test on the LVDS cable to find out if you have all the wires ok

Let us know .

[wang890]

Re: Replaced Inverter and CCFL still no backlight

you are getting too technical now. hehe

where is this keyboard controller?

i do have a power supply i built in high school. goes from 1.2v to 30v. still working and i can use that to "inject" power but where?

i think we are getting somethere. i haven't heard the inverter can be disabled. quick google search did not yield any result on how to re-enable inverter.

[vinceroger69]

Re: Replaced Inverter and CCFL still no backlight

i think what hes trying to say is that you need to remove only the Enable cable from the inverter board socket should be one wire to remove i guess and inject voltage onto the inverter board socket where you have just removed the wire from if it all works the fault maybe the kb controller ive not worked on laptops much but thats how im reading his instructions to you.

[highpulse]

Re: Replaced Inverter and CCFL still no backlight

as vinceroger mentioned is practically that , so if you have a machine with INVERTER , then you must have a control IC that will ENABLE or DISABLE the inverter (or else if this don't happen , imagine you shut down your machine , if there is not a IC to control the inverter than your screen would stay always with full brightness .
So main cause making inverter not to working properly are:

KBC (keyboard controler ( usually ITE , WINBOND ; ENE ; NUVOTON ; SMCS ) in this controller there is a part (pin that send a SIGNAL 3.3 volts usually to ACTIVATE OR DISABLE the IC on the inverter .meaning that you can have 19 volts on the dc in of the inverter , but its the IC that controls the inverter(this ic im speaking now its on the inverter itself)don't receive the ENABLE pulse then it will never start.

another problem can be LVDS cable (cable that goes from motherboard to the inverter and screen) chek with a multimeter on continuity mode (BIP (noise) ) one probe on first pin of inverter socket the outer probe on the main cable that connect to the motherboard ( would be nice here having a schematic for you to know were to put the probe in the main connector on the board .

in some very rare cases , i've seen gpu bga's making this trouble (but once again very rare)

also pay extreme attention near the KBC controller and near the LVDS connector is you notice broken or burned trace , or if you notice any damaged components.
let us know

[wang890]

Re: Replaced Inverter and CCFL still no backlight

ok. i will take a look to see any burnt mark on the motherboard where the harness connect between motherboard and inverter and report back.

i got the laptop without keyboard, memory, hard drive, dvd, wireless, smartcard, modem, 3g card, hard drive tray. i collected all these.

worst case is use it as a downloading "desktop" and media station.

but again i am not giving up yet if if i blow the whole thing up.

so is it ok if i touch the pink wire and white wire on some metal surface at the same time to see if there is voltage?

when the first day i got the laptop i was trying to fix the battery latch which broke as well. i was fixing that while computer is on and i was pushing a pin with a screw driver and accidentally touched something on the board and a little spark and computer shuts down. booted ok next time and checked everything still works fine. hape that doesn't have anything to do with this current condition.

what about split the wires to the overhead LED and hook up a bunch of white LED or some strip of light in place of ccfl? i guess that way backlight won't turn off.

when you close the cover of an lcd does it turn off both the lcd and ccfl or only ccfl? i just realized recently lcd without ccfl doesn't use any battery pretty much.

[wang890]

Re: Replaced Inverter and CCFL still no backlight

I'll take pictures and put on my photobucket and link them here too. gonna spend all day on it tomorrow. not working.

[trebo]

Re: Replaced Inverter and CCFL still no backlight

so is it ok if i touch the pink wire and white wire on some metal surface at the same time to see if there is voltage?

if you are talking about the wires to the CCFL tube, DONT do that, they are high voltage

[highpulse]

Re: Replaced Inverter and CCFL still no backlight

yes don't do that !!! if you're not comfortable with electronics i advise you to let a professional do this for you .
like i mentioned ,its better if you get first a schematic for you can chek the correct parts to measure before you can damage more .

[fddizon]

Re: Replaced Inverter and CCFL still no backlight

DON'T DO that bro... it CAN KILL you...

did you trace how far the voltage go from inverter board socket?
it passes a fuse. i came across with the same issue and found out inverter fuse is busted.

[wang890]

Re: Replaced Inverter and CCFL still no backlight

yeah, not gonna touch lol. still alive.

ok I took some pics this morning and tried many things.

1. research shows using 9v battery can supply power to the inverter, didn't do anything.
2. using my high school built power supply, supplied voltage. didn't do anything, the inverter got warm.
3. found the yellow wire on the harness which supposed to be the 12v and that is the first wire. measured voltage there is 19v. measured both with my multimeter and the high school power supply which can measure voltage as well. (glad I am keeping this thing)

let's see if pics works. first shows test set up, second shows how I hooked it up for the measurement and power supply. third one shows the LED works from inverter board when computer is powered up. but I can't light up this LED with supplying power to inverter.

maybe I should get another ccfl. this one could be bad. I didn't test before leaving positive feedback on ebay. but I can't be certain that one is bad. unless I buy a tester thing on ebay which is 5 bucks it's ok.

I was looking for this fuse but not sure which one is fuse. I see the ambient light sensor. I will go measure some more see where it stops. but I am a little afraid to poke every lead. last time I tried to fix a tv I found in the trash and touching my meter somewhere and huge spark scare the crap out of me.

[trebo]

Re: Replaced Inverter and CCFL still no backlight

the component in your second picture, along the bottom row next to the connector, under the brown capacitor is possibly your fuse, they usually have a letter or a number on the top of them
old broken screens usually have ccfl still working in them, can you get hold of one of them to test

[wang890]

Re: Replaced Inverter and CCFL still no backlight

no voltage in half of the thing there:

what to do next? check connector on motherboard is loose or input some voltage directly to the solenoid and see if get 600v on the other side?

[vinceroger69]

Re: Replaced Inverter and CCFL still no backlight

can you post some good clear pictures of the board up so we can really zoom in on them and see the parts correcty theres a small white part that maybe the fuse bottom right under the ground screw hole you have been using

[fddizon]

Re: Replaced Inverter and CCFL still no backlight

probe on that white part they mention. if this is the fuse, then you should get 19v on both ends.
if only one has 19v, you know what to do.

[wang890]

Re: Replaced Inverter and CCFL still no backlight

here I see the white part there:

doesn't look damaged.

I have 2 inverters one is original another is ebay. they have different arrangements but both works on powering up the LED.

clear enough? I am just using my phone to take pic. don't have a micro lens but have big lenses and big camera. lol

[wang890]

Re: Replaced Inverter and CCFL still no backlight

probe on that white part they mention. if this is the fuse, then you should get 19v on both ends.
if only one has 19v, you know what to do.

yes. just measured. white part. both side, 19v no problem.

[vinceroger69]

Re: Replaced Inverter and CCFL still no backlight

thats a very good picture can you do another pic towards the inverter itself so we can see parts and yes that white part reads ok imo

[wang890]

Re: Replaced Inverter and CCFL still no backlight

maybe the pulse guy is right. something to do with further down the line. keyboard control.

I am gonna take laptop apart and see what's going on.

[vinceroger69]

Re: Replaced Inverter and CCFL still no backlight

could well be ive just re read post 5 again.