Sorry to ask again but, got problems, wont start up.
 

OK, I apologise up front but I cant find a definitive answer, so a brief history;
My son used one of the usb ports to charge a toy indoor helicopter and after about 2 mins, his ps3 slim 160gb cech2503a 2 years old, shut-down and wouldn't start up.
The stand by light is on and when pressed it goes to start and gets green lights then shuts down. There is no flashing lights and only one start up beep. After it shuts down there are no lights until you repress the start button which then goes to standby again. It will not go into recovery and only does as described above. There has never been any modifications or flashing or firmware downgrades and only official Sony software upgrades. It was working fine upto this point although it was a lot over Christmas due to new games. Avice seems to be psu or power board, so I'm needing advice on how to test or trouble shoot with ammeter or whatever etc.

Does the light turn yellow briefly then go red?

No goes red to green then just white lights around buttons and off

the 4 pins cable from the psu would be:
1. SWITCH_ON (0v on standby, 5 or 3,3V on startup)
2. Ground
3. Ground
4. +5V

you could measure if the 5V is steady and still there after it shuts off, but since you can sort of reset the ps3 by pressing the power button again this might be useless to check.

you could also test if the fuses (marked by an F and TH) on the mainboard are still ok, and you can check if the ribbon cable from mainboard to power/eject board is not damaged, they seem to be brittle.

still a normal ps3 would give a blinking red light on faillure.

Btw, is the fan starting for a moment?

yes, the fan starts for a moment just as the green light goes on which is about a second then the light goes out and then the white backlights around the buttons stay on for 2-3 seconds then every thing goes off, until the button is pressed again.

it might be a coinsedence and due to overheating instead of the usb charger, because apparantly the usb ports are better protected then i thought....

ok tested the power from the psu and got 5.47v,0v,0v,4.6v with the ps3 in standby

funny that you read about 5V on the 2 outer pins, the switch_on pin should be 0V in standby and 5V on startup.

is one of the outer pins changing voltage if you start the ps3? , just curious...

no i tried that and when i turned on voltage stayed the same i expected one to change

this should mean the 12V is alive when the ps3 is in standby, really weird, but maybe i'm just loosing it.

you can only measure the 12V on the fan connector or the metal prongs.

but the 12V alive or not, don't know if it would be a problem for the booting order...