Forum ELVIKOM

Hi,

Sorry, had to intrude the forum to wake up a dead topic.
viewtopic.php?f=213&t=21951&hilit=Lenovo+E520

As it's closed, i made a new one and continue the saga.

I happen to have the same problem. Already replaced the LCD chord and troubleshooted through the table in the previous topic.
In my case the other readings were fine, but pin no. 19 on LCD1 was showing nothing/short. I managed to find the problem with q4901 transistor. The 32. pin of U2701A (NPCE795GA0DX ) seemed to lead there and gave absolutely nothing. When i tried directly from pin 32 (without the named transistor), then it gave me ~3.3V. So i replaced the tranistor from Q4901 and now the 19. pin of LCD1 gives out 0.02V approx.
Is the reading right? The LCD still has no backlight.
Also, the 7. pin is now dead. As i read from the other topic, it should give out at least something.

I'll give the readings below:
5- 3.3V
6- 3.3v
7- 0
8- 0

16- 3.3v
17- 3.3v
18- 3.3v
19- 0.2v

Thanks for trying to understand my messy text and helping me out, if you can.

Got it working.
Spent a full friday dealing with the datasheets and suggestions of my friend and the problem was quite simple.
Ignore the stuff about pin 7 - it should be an input.. from the display. So the voltage may vary and it's for controlling the LCD presence only.
There are pins 1,2 and 3 on LCD1. Their output voltage should be 20v from adapter and 10v from battery. Basically on the other side of the board, near SIM card reader, there are two caps. One is C4901 with a fuse F4901 - for the battery voltage. The other is C4903 and F4903 - for the adapter voltage. The screen was hit and something must have been shorted out, because the two fuses were dead. Repalced them and now the screen lights up.
Thanks for having this forum, tho. The topic i referred to, helped to get all the troubleshooting started.