03-16-2009 05:52 PM
I have a T60 with a backlight problem. I changed the inverter board, and it "sort of" worked: Worked reliably at low brightness, but if I turned the brightness above about 50%, the backlight would go off, which I could fix by suspending and unsuspending. Here is the problem - I replaced the inverter board with another one, but now the backlight doesn't come on at all with either of the two new inverters. (The machine still drives an external display just fine.)
My question: any thoughts on what might be wrong now? I would hate to buy a new panel and find out that wasn't the problem.
03-18-2009 03:30 PM
Short version: I think the backlight in the LCD is getting so old that it draws too high a current to successfully light up - this is based on the fact that you experiences similar behaviour with both inverters and that the CCFL works at lower brightnesses. But still, for how long has the LCD been used?
As the CCFL backlight is used more and more, spatter deposits (fine grain metal) is deposited to the inside of the CCFL bulb from the electrodes existing at each end of the CCFL. This spattering occurs due to the decreased amount of mercury and ignition gas available in the CCFL depletes onto the phosphor layer (outer "white" layer of the CCFL inside the glass) by adsorption. This is why you will see that old CCFLs usually look very dark near the ends.
The electrodes ignit a gas (usually argon) which makes the "loose" mercury emit UV light. Phosphor lights up as bright white under UV.
When enough argon and mercury is depleted deep into the phosphor layer, the CCFL will require a higher and higher electrode voltage to ignite. When trying to power it on, it will eventually draw as much current as it can.
The inverters in all laptops are current limited, which means that the CCFL cannot draw the current it wants - which is a good precaution, since old CCFLs would otherwise become red-glowing at some point due to heat.
03-18-2009 03:47 PM
Thanks a lot for your reply. I think I have a much better understanding of the situation now. In response to your question, the machine is almost 3 years old, and it generally runs 24 hours/ day, although I generally turn the brightness all the way down when I am not using it.
It is worth trying to replace the CCFL? I am not the best with a soldering iron, so generally I go to the local TV repair place and have them do the wet work for me.
03-20-2009 04:50 PM
Got too busy with work, so i didn't have any time to check out the forums,
But another thing which should be checked first actually, which i didn't think of before now - Is the LCD cable in perfect working order? Take a close look at the junction on the flex cable, where the part going to the inverter splits from the main cable - are there any visible damage, like torn edges and thus broken connections?
If the flex cable looks fine, then i'd say it is definitely the CCFL.
Typical MTBF figures for the CCFLs used in laptops is around 20,000 hrs. For some reason, it is not stated at what relative brightness level this is measured at, but i suppose it is the maximum intended. 20,000 hrs is approximately 2 years and 4 months of continuous use, and you should also take into account heat generated by the inverter next to the bottom of the LCD which will also decrease life.
But still, i think that your CCFL died relatively early if it spent a good deal of it's life at a low brightness.
Replacing the CCFL is hard to do - they're stupidly fragile, and you'd likely need to re-use the current wires going to the inverter. It typically involves taking apart the LCD panel assembly, as illustrated here: http://www.laptoprepair101.com/laptop/2007/12/09/r
I'd recommend using some qualified business for this, not because the ccfl replacement is impossible as DIY, but because of dust particles in the room. They're just everywhere.
03-20-2009 05:02 PM
You are probably going to laugh at me, but I a few days ago I received an email saying that my warranty would expire in 30 days. I have a few Thinkpads, but sure enough, it was talking about the T60. For some reason, I thought I had checked and it was only a 1 year warranty.
Next question - when I send it back, will they figure out that I have opened the display and refuse to cover the repair? Actually, I don't even have the original inverter board as I replaced it with a working but used one I bought a few months ago.
If they don't cover the repair, I guess I will check the wires again and then bring the panel somewhere for repair.
03-22-2009 03:50 PM
Hah, now that is actually funny
Unless you really messed with the screws, so that it is visible, then no i don't think so - except - the doubled sided tape on the LCD bezel and LCD bottom frame is likely not intact any longer, so that might be a problem. They're not going to see it from the new inverter. No matter what, i'd send it in for service. You have not damaged anything at all, not on purpose (for fraud) and not even by accident, so the thought of sending it in shouldn't leave a bad taste in the mouth at all.
But if they determine you have tampered with it, then you'll have to accept that unfortunately.
03-15-2010 09:40 PM
Hi, I'm having the same problem -- replaced, and blew, three inverters now. (the first two were pulls so I thought they were bad. Then I bought a new one and blew it).
Please let me know if you have any luck at all with your IBM Service Contract. I would love to see what they have to say about this problem.
I used to love IBM service, but the one time I tried to use it with my t60, first they refused to service it, then they serviced it and it came back worse than I started, and when I sent it in again, I was told I should have had an accident plan.
So even though I bought a three year contract, ever since then, when something breaks, I order a new part and fix it myself. Except this really has me stumped. I have seen messages about our same problem in other forums on the internet also, but have never found one where it was resolved.
I'm sure they'll tell me it's my fault. That's their first line of defense. Plus I cracked the frame a bit opening and closing it so they'll say I dropped it.
I get nautious just thinking about sending it in and I won 3 IRS audits, that's how impossible they were and how much time it took.
But if they repair yours, and you report back what's wrong, I'll get the right part this time and repair it myself.
Good luck, my friend, and many thanks!