Measure the power consumption (in mA) of the board in the following cases without battery connected:
a) Board turned off (before pressing to the power button).
b) Board turned on with RAM memory connected.
c) Board turned on without RAM memory connected.
Since the board doesn't work with your service power supply, you need to cut the Red or Black wire (one of them) between the DC socket and the motherboard and connect an ammeter between both ends of cut wire to measure the power consumption.
An alternative option is to use a "clamp" meter. This way you can measure the current without cutting the wire.
In this case you can measure the current at points "b" and "c" only, since such a meters usually can not measure low electrical currents.
a) Board turned off (before pressing to the power button).
b) Board turned on with RAM memory connected.
c) Board turned on without RAM memory connected.
Since the board doesn't work with your service power supply, you need to cut the Red or Black wire (one of them) between the DC socket and the motherboard and connect an ammeter between both ends of cut wire to measure the power consumption.
An alternative option is to use a "clamp" meter. This way you can measure the current without cutting the wire.
In this case you can measure the current at points "b" and "c" only, since such a meters usually can not measure low electrical currents.