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Old 05-02-2012, 08:59 PM
Comtech Solutions Comtech Solutions is offline
 
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Default Laptop LCD repair question

Hello technibblers. Has been a long time since I have posted! I recently invested in the podnutz laptop repair videos and decided to try my hand at hardware repair.

Here's my latest challenge.

Toshiba Qosmio F10 laptop. LCD screen has reddish tinge when powered on. Blinks for a moment then turns off. Connected to external monitor works fine. Very faint image on screen. This occurs with the laptop apart, so it's not an issue of pinched wires or poor connection.

I am thinking that this must be is an inverter or bulb problem.

I have a known good screen with a good bulb and bad pixels. I disconnected the HV harness (2 wires, 1 pink, 1 white) from the laptop's FL inverter and plugged in my known good one. My known good one lights up, leading me to believe that the laptop's FL inverter is good. However, the laptop's screen fully lights up and as well (at the same time, so both are lit up) and seems to be working perfectly and this has me confused as to what to do next.

Anyone with experience who could offer me some sage advice - it would be greatly appreciated.
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Old 05-02-2012, 09:51 PM
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What I don't get is the laptops screen fully lights up as well. at the same time.

How can 2 laptop screens light up at the same time, when there is only one inverter and one harness?, unless I am missing something, or mistaking something.

Easiest thing to do, is a simple checklist here.

Old screen - replacement inverter.
Replacement screen - old inverter.
Old screen - old inverter (just in case there was a loose connection on the harness).
replacement screen - replacement inverter.

One of the above has to work.

Also you mention a faint image on screen, is this with the external monitor, or the orig screen?
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Old 05-02-2012, 09:59 PM
14049752 14049752 is offline
 
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So, what's happening is you're leaving one CFL from the Qosmio's screen plugged in while testing. Then testing with another CFL (in a broken screen).

The screen you're working on has two CFLs in it. You're only unplugging one. By the sounds of it, you got lucky and guessed the right one.
(I'm assuming you unplugged the pink and white cables because that's what's on the broken screen.)

So, you can plug that one back in, then plug in your test screen where the blue and black CFL leads plug in. Probably both screens will go out now because you have a bad CFL plugged in.
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Old 05-03-2012, 10:47 PM
Comtech Solutions Comtech Solutions is offline
 
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Ok, thank you both very much.

@ Cadishead Computers-to clarify, the display on an external monitor is perfectly fine, it is the Qosmio's screen only that is faint

@ 14049752-I believe you are correct. You clearly have done this before

Please bare with me as I work through my methodology with each testing scenario.

There are 2 plugs on the Qosmio's screen; 1 is pink/white (p/w) and 1 is black/blue. (b/b). 1) With both unplugged, I get a faint image on the Qosmio's screen
2) With p/w plugged in and b/b unplugged, I get a faint image on the Qosmio's screen
3) With b/b plugged in and p/w unplugged, I get a faint image on the Qosmio's screen

Test screen has p/w only

4) With Qosmio's b/b plugged in and test screen's p/w plugged in Qosmio's p/w spot, test screen lights up and Qosmio's screen appears to be bright and working well.
5) With Qosmio's b/b unplugged and p/w plugged in and test screen's p/w plugged in to Qosmio's b/b spot, test screen is dark and Qosmio has faint image

6) With both of Qosmio's b/b and p/w unplugged and test screen p/w plugged in to Qosmio's p/w spot, there is no light on test screen and a faint image on Qosmio.
7) With both of Qosmio's b/b and p/w unplugged and test screen p/w plugged in to Qosmio's b/b spot, there is no light on test screen and a faint image on Qosmio.

Does this mean that the diagnosis is a bad cfl (the one attached to the p/w wire)? So replace that CFL only? I still can't understand why scenario 4) has the Qosmio's screen lit up - that would be the 1 inverter board then (the one the p/w plugs into), no?

Thank you in advance.....
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Old 05-03-2012, 11:40 PM
14049752 14049752 is offline
 
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I'm still opting to go with bad CFL. It's up to you if you want to replace the CFL, I find it to be a pain in the butt and not at all worth it...especially on dual CFL screens.


Quote:
7) With both of Qosmio's b/b and p/w unplugged and test screen p/w plugged in to Qosmio's b/b spot, there is no light on test screen and a faint image on Qosmio.
This is the only part that calls my guess into question. Some dual backlight inverters will not function unless they have one (usually the pink/white) or both backlights plugged in to a good CFL. If you have two test screens available, try both at once to rule out the inverter.
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Old 05-04-2012, 03:37 AM
Comtech Solutions Comtech Solutions is offline
 
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Ok thanks.

I am looking for an additional screen to test with. I have taken apart a compaq and an acer so far this evening, but both have different connection types, so I might have to dig far deeper in my pile of, ahem, junk to find a working lcd screen with the same kind of plug-in.

All my reading tells me replacing ccfls is doable, but is a pain. This laptop has some specialized software that would make a repair worth it, unless the cost exceeded $200 (Canadian or American). Unfortunately, I am already into this laptop for $150 (purchase price), and $100 for battery and ac adapter. A quick search of ebay shows me that the dual inverters are available for approximately $15, and the full LCD screen (used) can be had for $100-$150 (ouch!!) delivered to me in Canada.
Because scenario 4) has the qosmio's screen lit up, I'm tempted to spend the $15 and try the dual inverter. But I'm going to keep digging in my pile to see if I can find another good lcd screen to try first to confirm the theory on 7). I will post any efforts I make.

I do really appreciate you following me through this repair and my learning process. If you were closer to me, I'd gladly pay you to make the proper diagnosis This one's bugging me already!
I'm a star with desktops and with Windows and if I can ever offer some sage advice, I'd be more than happy to.
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Old 05-04-2012, 06:39 AM
gazza gazza is offline
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I agree, replacing the bulb is a pain, not worth the hassle.

May I suggest a tool that I use to test LCD/LED screens, you will find it here http://www.lcdparts.net/LST01.aspx.

It will save you time and money.

As for the red tinge that's coming from the bulb. Just replace the screen.
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