Review on 🔌 YaeCCC Auto Voltage Transformer: High-Quality AC Variable Voltage Converter for Reliable Power Conversion - 110VAC Input, 0-130VAC (500W) by George Mack

When testing mains powered electronics you must work with 120VAC above and below normal. This device can operate on AC power from 0 to almost 150 VAC. You can safely monitor the current (clamp ammeter) when the voltage changes. Replacing the fuses with items that short out off the normal line, 120 VAC, saves. Follow the current-voltage curve from zero and keep it at a safe level by finding the problem in the Device Under Test (DUT). I also use a CVT to ensure the repaired units can handle low and high voltage levels of at least -+10% (-brown outputs / +spikes). This Variac does everything the $1000-plus units do. may not last a lifetime, but I'm an old dude!