Use a power supply with 12V and current limitation (300mA)

Connect Pin 2 and 3 of the socket with a 1k resistor. This activates the integrated testprogram.
Set the oscilloscope to 1ms/div.

Mega1
After you have connected the power supply unit, at pins 1, 2, 27, 28 30 and 31 of the Mega8 you should see the 5V square wave signals with the oscilloscope.

Mega2
After you have connected the power supply unit, at pins 1, 2, 27, 25, 27 and 28 of the Mega8 you should see the 5V square wave signals with the oscilloscope.