T42 screen intermittently going dark

The screen on my wife's T42 suddenly goes dark. Whatever is on the screen is now just barely visible. I checked power management settings and nothing there to explain this behavior. Doesn't seem to matter whether it's plugged in or operating on battery.

If I put the computer in sleep mode (Fn+F4) and then wake it up, the screen comes back on normally. This seems to rule out a bad connection. This behavior started a couple of weeks ago, initially every few days, then every day, and today, she can't use it more than 10 minutes without the screen going dark.

I've done a couple of previous repairs including removing the LCD front bezel, so I'm comfortable replacing components, but I'd appreciate some advice isolating the problem.

I suspect it will, but good idea to verify. I have it set up now with both monitors running. Of course, it stops acting up when I'm trying to troubleshoot.

Ok, it started acting up again and the second monitor was unaffected.

Since moving the computer around and tilting the screen seem to have no affect on the intermittency of the problem, I'm betting it's not a loose connection.

I just read elsewhere in this forum that the inverter for the screen lamp is a likely suspect. I found a replacement inverter online for less than $10 (new), so if I'm going to open the case up and remove all the FRU's to even access the screen wiring harness, I might as well replace the most likely part, no?

Anyone know of any other failing part that might cause this behavior?

Replacing the inverter solved the problem... for a while. Last week the screen went permanently dark. This time I could see what appears to be the LCD bulb flickering in the lower right corner of the screen accompanied by a popping sound. Not good. So I disabled the LCD display in the BIOS to protect against ancillary damage. My wife had been using an old Gateway CrystalScan 1024 CRT (remember those?) until I was able to obtain a replacement LCD.

I decided to purchase an entire T42 monitor assembly with inverter, etc, to save R&R time. When I received the replacement and swapped it out, I had to reactivate the LCD display in the BIOS. Unfortunately I made the mistake of setting the BIOS to LCD-only before checking out the replacement. Opps! Turns out it was DOA (dark). I can barely, I mean barely see the desktop is displayed... same as the original monitor. Fortunately the seller has money-back policy. But this means I can't reactive the external monitor from the BIOS because the screen is too dark to navigate the AcessIBM and BIOS menus. The wife is NOT happy since she can't use the laptop until I can purchase and install another display.

It just occurred to me that if I disassemble and disconnect the CMOS battery for a few minutes, the BIOS will be restored to factory defaults. Can someone confirm if the default display setting is "LCD + VGA"?

At the time, I didn't remember the FN combi. I panicked when I heard the bulb popping and wanted to be quick about it, so I rebooted into BIOS and took care of it there. That wouldn't have been a problem if I had been stupid about turning off the VGA.

It would be good to get a confirmation on the BIOS default before I spend a couple of hours disassembling to access the CMOS battery, and reassembling to test. Then I have to go through the whole procedure again again when the next replacement arrives). . Sigh.

The only manual I have is the repair manual. I think there's a reference in the AccessIBM program, but it doesn't do much good without a screen. Anyway, I figured out that by shining a reading lamp on the screen, I'm able to see well enough to navigate to the BIOS and reset the VGA display mode. So at least my wife can use the computer until I can get another monitor.

Thanks again for the help.