MacBookPro won't boot, no activity but power seems good.

Hi,

My MacBook Pro mid-2009 (model A1297) doesn't start anymore without any reason (no fall, no water poured on it, no accident ever occurred with it).

The power button doesn't start it up. No activity, no fan, no sound (no chimes), nothing...

BUT: the battery status button indicates the charge of the battery, and one small red led is blinking when plugging the MagSafe, and the MagSafe lights on the right led (green when battery is full, orange when not).

The power button doesn't seem to be at issue, as I can still use it to reset the SMC (I can see the light on the MagSafe switching from green and then orange during the reset), and I can also use it to disable the battery (same as SMC reset, but holding it all 10s, and then release everything except power button for another 10s, and then the battery status button is disabled, and plugging the MagSafe shows the battery lights moving, and to reenable it I just hold the SMC reset combination for 5s).

I tried to short the PWR jumper on the logic board, but no more results. I checked the voltage between these pins, and got 3.40v with the battery connected.

Is it something else to check?

I also already tried to launch with and without the battery, the RAM... no change...

Do you have ideas?

I suspect something wrong with the logic board, but how to determine it?

Thanks for your help.

Best regards.