Mega 2650 output voltage

I am having trouble with Network adapters failing. The network adapter calls for 5v input. I checked the Mega 5 volt output pin and find it is only outputting 3 volts. Yes it is the 5 volt pin. Checked the 3.3 volt output it too shows 3 volts.
Voltage input to the Mega is 4.90 volts.

How are you powering the Mega?

cheap chinese or real deal?

(deleted)

I see you are measuring the voltage of that pin, be wary that it has a limited power capacity. 4.9V seems a little low, too low for the Vin, Arduino recomends 6V.