brazman :
I have a Sony Vaio model PCG-61611L and tried all of these suggestions and none worked. I pressed the power button and the power LED would come on, CAPS LOCK, NUM LOCK, AND SCROLL LOCK LEDs would flash then it appeared that nothing else happened. I could open the DVD/CD drive and this is what appears to be my issue. Turned Laptop off then back on and immediately pressed the DVD/CD eject button and the system powered up. Leaving the tray ejected seemed to solve my issue. Went into BIOS and set default boot to hard drive and now it appears to be functioning. I'm not fully convinced that I have solved my issue due to how it acted previously. Just as you stated it would work sometimes with no issues then there are times it took awhile to get it to power up. I am hoping that I was experiencing some kind of conflict with boot selection and that this may be a solution. Hope it works for you.
Brazman!! You have helped save my sanity!
I have been trying for days to troubleshoot my neighbor's laptop but after completely disassembling the machine and examining / testing everything I could find nothing wrong! The model is the same as yours: PCG-61611L ON THE BACK and VPC23EEFX ON THE LCD's BOTTOM CORNER.
The symptoms were the same: Power LED works, All other LEDs would flash once, No power to anything important (HDD, Fan, LCD) but the DVD drive and USB ports had power, and the CPU WAS HOT.
The motherboard appears well-soldered & undamaged. I unplugged everything except the DC power jack and the fan, and made it my goal to get that fan to spin! The CPU was hot so I set up a secondary fan to keep it from overheating, then I poked and prodded everywhere I could think of, taking breaks to read different hardware forums, and you know what finally worked? Yep, connecting the DVD drive, pressing power, then immediately ejecting the DVD tray...not a moment later, the fan started to spin, then there was some activity on the memory card reader's LED.
So, good sir, my question to you is whether your BIOS tweaks have made your system stable again and whether you have any further advice. I'm a little afraid to put the whole thing back together not knowing if there may be something else I need to investigate. I'm still curious about the OP's "turn switch" that had to be set to "unlock"...if that is for the CPU, as rbbnsx4 claims, then setting it to unlock doesn't seem smart...
I appreciate the help tremendously, to all tomshardware supporters and members. Thanks guys!