T61 Video issue

[jvarga]

I'm trying to diagnose a T61 laptop for a friend of mine. When I received it there was no video (even on the external VGA output). So upon searching google I found out about the nVidia video issue. I have replaced the motherboard which seems to have fixed the video problem (external video is now displayed) but the lcd screen on the laptop is dim. I can barely make out some windows. I now suspected the inverter or the CCFL's. I tried doing a trick which I saw someone else do in measuring the RF freq with a DMM near the inverter card. It works on a different laptop (freq is around 22kHz and is varied up and down with the brightness control. I do not get an freq output from the board on the T61. I also read where the AC output to the CCFL's appears to be around 600V's. I tried to measure this with my DMM which will measure up to 750Vac. No output again (well actually it measured 1.5Vac). I'm concerned that the new motherboard I got is not sending the proper voltage on the proper pin to the inverter board (41W1338). Does anyone know where to measure this? I assumed that I had DC input because the LED's lit on the board.

Thanks for reading.

[ajkula66]

Welcome to the forum!

Your "new" board may be bad as well. I'd try testing the laptop's LCD on another machine/planar.

Good luck.

[jvarga]

Yes your right, I put my old board back in and viola the backlight was working again.
Looks like I need to find another replacement. Any suggestions on models? I've seen 42w7651 and 42w7875 with the CPU.

[ajkula66]

Send a PM (private message) to forum member TuuS - he usually has good, fully tested T61/p motherboards available.

[Cigarguy]

^^^ X2 to above recommendation.

[jvarga]

Thanks for the advice. I'll contact TuuS