At the top middle of the back of the VinoTemp is the circuit board. On the right side is the high voltage (120 VAC, 160 VDC).

On the left side of the circuit board is the low voltage, 12VDC. But the voltages can be around 10 or 11 VDC

The picture is of the left side, which is where the VinoTemp troubleshooting guide says to do your checking, using a Voltmeter.