Laptop boots then turns of with flashing power button light

[Cd86]

Hello

Was using laptop when screen went blank and power (on/off) button starting blinking blue. There was no pause in the blinking just a steady flashing on and off. 

Rebooted laptop and signed into Windows 10bthen after 3 or 4 minutes same thing happened. Screen went black/blank and power button led started blinking continuously.

Caps lock button does not blink only power on/off button.

Tried pressing power button continuously to force shut down but continued to blink. Have to wait for it to stop blinking on its own.

As laptop does boot but only for a short period is this a motherboard issue? 

Thanks

Powersupply is connected and power light on and tried on another laptop and works fine.

Removed battery, ram and replaced button cell battery on motherboard but same thing happens.

Removed hdd and plugged into another computer and can access files on hdd. 

Tried to restore to an earlier point but laptop screen goes blank and power on/off led blinks

Tried to use win10 recovery media but same thing happens

Turned back on and same thing happens. Can log onto windows but after laptop has been on 4 or 5 mins screen goes blank and power on/off led blinks. No other keyboard buttons flash. 

Laptop battery doesn't hold a battery for long and always use power supply.