15R 5537 i5 won't power on / no POST

When I press the power button, the only response is LED1 (power LED) in this sequence:

ON 10s, OFF 4s, ON 10s, OFF 4s, ...

There is no beep, no sound, no fan, nothing on the screen. I've tried all these suggestions:

• remove battery
• remove hard drive
• remove DVD drive
• discharge built-up static charges
• reseat RAM
• put RAM in only one slot
• reseat heatsink (CPU is soldered on - cannot be reseated)
• put in another set of known good RAM
• swap out CMOS battery
• BIST
  
  • Hold key D while pressing the power button
  • Hold key Fn while pressing the power button

Any idea what the problem is? Anything else for me to try/check? Please help. Thanks.