How to measure the failure( CPU or BIOS)

[Jane11]

From time to time I need to repair a Linux embedded device that is
totally dead.
All voltages are correct on mainboard but yet, the device does not
start.

So, I think 3 reasons are possible

1.Faulty CPU
2.Faulty BIOS
3.Faulty PCB

How( what pins ) to measure to know it is No.1 or No. 2. or No. 3?
Any suggestion?
Thanks

 

[alec_t]

The first step would be to gather all info you can about the device (pinouts, IC datasheets).
Check voltage at the device' supply pins.
If you know how the device should function then use a scope to check for expected waveforms/pulses at output pins.

 

[eTech]

From time to time I need to repair a Linux embedded device that is
totally dead.
All voltages are correct on mainboard but yet, the device does not
start.

So, I think 3 reasons are possible

1.Faulty CPU
2.Faulty BIOS
3.Faulty PCB

How( what pins ) to measure to know it is No.1 or No. 2. or No. 3?
Any suggestion?
Thanks

What type of device?

Does is have a "clear bios configuration" jumper?
Usually a three pin header...