OK, I may have a solution here ..... I have been servicing an Inspiron N5110 Laptop, it has been the bane of my life up till this morning. Last night I replaced the CRT and Power interface PCB unit. On connecting the AC adapter after re-assembly I got a strong charging light on the front panel. Initially it would not start so I removed the Keyboard again an proceeded to short the pins around the power-switch connector. suddenly the system came to life and booted normally. Reassembled the Unit, putting back all screws. Shutdown and restarted the laptop several times, there seemed to be no problem (NB: I knew the battery could no longer be relied upon). Then used the system for about an hour before shutting it down and going to bed. I left the AC adapter connected to the laptop.
In the morning I no longer see a charge light on the front panel, the bastard wouldn't start. Completely disassembled the laptop again, removed the CMOS battery and shorted the terminals for well over a minute. Partially re-assembled and tested for powerup (I left the main battery removed from the system). Tried repeatedly to spark it back to life like it did the night before. Gave up and went scouring the WEB for a solution, that's when I made that early post.
Whilst researching, I had left the laptop in it partially disassembled state and with the AC connector attached. Suddenly, through no action of my own, the system came alive, a protesting beep as I had once more removed the CMOS battery. System stablised after reseating the CMOS battery. I pulled out the AC adapter and made a loose reassembly of the laptop. Reconnected the AC adapter and pressed the power switch, up it came, and it remained consistent. Now, my theory is that the main battery, in its dodgy state, had somehow corrupted the system overnight with the laptop remaining connected to the AC adapter. Now, with the Main battery removed and the CMOS battery removed, but the system still connected to the AC adapter, with all the efforts to clear CMOS, the system had slowly recovered itself from a convoluted state of hybernation brought on by the dodgy battery.
Trust this long description will help someone out there pulling their hair out over a N5110 ..... Cheers