Progress Direct Systems Volt Tattler 2 Owner's Manual page 38

Regulator Issues
Test the voltage on the positive lead of C7. It should be 3.3V. Next check the non-ground lead of C8. It
should be close to the input voltage. Check the Gnd lead of the regulator (LP2950, KY5033). Any voltage
here contributes to the power to the microcontroller. Gnd must be close to 0V. The "In" pin of the
regulator must be close to the input voltage. If not check Polarity Issues.
Polarity Issues
With the positive lead of the voltmeter check the voltage both at the Drain and Source of Q1. Both
must be very close to the voltage that we are watching. Below is a drawing of Q1 pins.
In normal operation Q1 is turned on so there should be little voltage difference between the Drain and
Source. If Q1 is not turned on check its orientation along with R6 and C5 for solder bridges and bad
solder joints.