ZX Spectrum Repair – Post Plugin Tests
With power in and switched on put your multimeter into DC measurement mode with a range of 20mA by using this icon:
Then put the black probe into the centre of the power jack
We are going to measure at two places, first the actual power jack, to the left of the jack is a point, press the red probe to this and you should measure 9V-12V. This shows that the correct power is coming into the machine.
And then measure each leg of the Voltage regulator, keep the black probe in the centre of the power jack and then measure each leg as the image below:
Bottom Leg: 9v
Middle Leg: 0
Top Leg: 5v