Never even seen a picture of one until I looked at the online user manual just now.
Is this unit one you've just acquired and are trying to fix or is it one you've been using, ie any prior symptoms or just sudden death or don't know?
STBY/AUTO switches it on? The button looks like it might be the soft type with a carbon pad on the back. They often fail after long use, just like your TV remote
. Clean the carbon pad. Bridging that button's gold contacts on the board will switch it on if that is the cause.
If the buttons are plastic and you feel a little click when you press them they're a different type.
No schematic in the operator manual and can't offer much else without one except to check everything with a magnifying glass.
I didn't look everywhere for a service/repair manual, maybe you can find one.
Not worth bothering if any circuit boards are potted - makes repair close to impossible.
On another forum somebody was helped to fix a laptop
when he posted some perfect close-up photos of the motherboard and a thorough description of the fault. That's rarely possible though and need to be able to read the id markings on even the tiniest devices.