Sony Vaio VGN-FS415 no start no LED

[apenir94]

got to repair this laptop from a friend, when pressing power button nothing happens, no LED no sound. Only after removing the back cover sometimes it started up again.
Finally found out that the lid switch being in closed position even after opening the display panel disabled power button. It seems that the mechanism holding down has a too weak spring but also the lid switch itself was too sensitive.

For an intermediate workaround I just shortened the tiny lever on the switch by about 1 mm. (could not get a replacement for switch SW6 type MPU-101-81)

It took me many hours to track this down, disassembling ~10 times completely ...