I’ve had a Dell Latitude C840 for the past 4+ years now. It’s big and heavy, but I absolutely love the 15″ UXGA display at 1600×1200 resolution. It’s crisp and readable and bright. Until, of course, this past Thanksgiving weekend, when it went dead.
At first, I didn’t know what broke and in opening up the laptop, I managed to break a few of the delicate traces on the flex cable that connects the display to the video card on the laptop. A quick search of eBay turned up a replacement for $15. That arrived yesterday and replacing it was easy. Reconnecting the display, I discovered that there was an image on the LCD, but it was completely dim–no backlight, at all. In a sense, this is good news: an entirely new display assembly goes for $150-$200 on eBay, but the display itself is okay. The problem could either be in the CCFL (lamp) or in the power inverter.
How is this good news? The specific display I have is the Samsung LTN150U2-L02, and according to lcdpart.com, the suitable replacement CCFL is model MS20305, $9.99 (plus $9.99 shipping). Of course, the lamp could be just fine and it could be the backlight inverter that’s busted, which could be replaced by Ambit J07.027.P.00 for $39.99 (plus $9.99 shipping). (Note: The inverter that’s currently on the display is labeled “AMBIT REV:2 K02I051.00″ and “LTN150U2-B”.) Both amount to less than the replacement of the display assembly, of course.
The downside here is that there’s no easy way (that I can think of) to test whether it’s the CCFL or the inverter that’s gone bad–or, worst case, both. Laptop Freak had a similar idea, trying to test the inverter with a multimeter, but the output from an inverter is typically in the range of 1,500 VAC which is both dangerous and outside the range of the average multimeter. The folks at Endicott Research Group published a great whitepaper on backlight inverters: Design Issues in the Selection of Backlight Inverters (PDF). In it, they explain how CCF’s work and how they test backlight inverters and how sensitive the tolerances are for proper operation. I’m guessing it’ll be cheaper to buy a replacement CCFL and hook it up to the inverter to see if it works than it would be to fiddle with the inverter and risk breaking it in the process.
Throughout all of this, I kept trying to think of people I knew who were hardware geeks who could help me troubleshoot this and I realized: as many online communities that I’m a part of and as many people I know, I don’t know any hardcore hardware geeks. I mean, I know plenty of folks who fiddle around and delve deeper than your average “I’ll just buy it at (insert electronics chain store name)” consumer, but that’s about it. In the upcoming year, I think I know what kind of new friends I want to make.