Thinkpads Forum

The first TP that I bought (used) several years ago is a 600E. It worked fine for a year or two and then developed a problem that I couldn't fix. It was put up on a shelf after being replaced by a 600X but now I'm ready to tackle it again.

The problem is that the LCD backlight takes somewhere around 3 to 6 minutes to turn on. I have replaced both the LCD panel and the inverter separately. Each time the problem remains, no matter what combination of old/new LCD or inverter I used. The only conclusion I can reach is that the problem is in the motherboard. Without fail, the backlight will always come on, it just takes several minutes to do so.

Video out the VGA port is active when it should be, as well as the video going to the LCD. I can shine a flashlight on the screen and see it. It does not seem to be a thermal (warm-up) issue as I have left the laptop on for an hour with the backlight working, turned it off and then immediately turned it back on and the backlight still takes several minutes to return to life. Also, if I toggle the video display modes (Fn+F7) between the three settings, the backlight turns off when only the VGA port is active, as it should, but then takes several minutes to turn back on when the LCD panel should be active.

I've tried searching the archives and not found any similar articles. Has anyone here experienced this problem and if so, what was the cause and the solution (besides replacing the motherboard)? Thanks!

Just curious, what are the specs of your power supply? (ie. 56W)

Most likely, it is the system board, but I am just wondering if you are getting enough power to the inverter.

If it helps, the system boards are pretty cheap nowadays...especially compared to the LCD that bought as a replacement.

tfflivemb2 wrote:Just curious, what are the specs of your power supply? (ie. 56W) Most likely, it is the system board, but I am just wondering if you are getting enough power to the inverter.

56W power supply. Also the same problem occurs when running only on the battery, but it doesn't seem to take any longer (or shorter) for the backlight to finally awaken. "Power to the inverter..", hmmm, maybe I'll check the connectors and ribbon cable to see if there is any excessive resistance in the line.

If it helps, the system boards are pretty cheap nowadays...especially compared to the LCD that bought as a replacement.

I might go that route but I've already got a stable of 600X systems that I've invested in. I was thinking more of getting the 600E fully functional and then selling it.

Edit: Now that I've fired up the 600E after all this time, I can sometimes hear a high frequency whine or whistle, something along the lines of a TV's flyback transformer. It's present when the backlight is off or on. This seems to point to an oscillator problem, which is basically what the inverter board is. Are the schematics available for the 600E/600X systems?

if youre talking about the hardware maintenance manual, its at ftp://ftp.software.ibm.com/pc/pccbbs/mo ... 9n1033.pdf ...if youre not, well then i just wasted your time!

dsigma6 wrote:if youre talking about the hardware maintenance manual...

No, I've got that already. I'm talking about the circuit schematics that detail every component used in the entire laptop and how they are wired together. It probably doesn't exist outside of IBM's (or Lenovo's) walls but I'd thought I'd ask anyway.

well considering the tawbook pdf and other simliar files are all from ibm ftp, i dont think its such a long shot that what youre looking for would be out there too.

You're correct. I am not aware of the schematics being available outside of IBM. I was looking for some schematics for a T23, when I was trying to diagnose a problem, and learn more about the PCBs.....no luck.

Given this community here, you can probably still sell the TP600E here for a decent price, without having to repair it at all. People here are always looking for "projects".

tfflivemb2 wrote:...especially compared to the LCD that bought as a replacement.

Funny you should say that... The LCD does need to be replaced as it has a one-pixel wide stripe of dead pixels down the right side of the screen. This was my older daughter's first laptop and I gave her a 600X as a replacement. Now her 600X has almost an identical defect, in almost the same spot on the screen. I wonder what she is putting on the laptop's lid to cause these problems ?