make a voltage divider using few series resistors. calculate the value depends on maximum out put current, or to draw few mA, measure the voltage between one of the series resistor that woulod give a range in your multimeter.
rather than giving a low input and measure, measuring at rated voltage would give a good result about its conditon. all depends on the purpose of your test such as to find turn ratio, or etc.
high voltage probe can be the best option if you can effort.
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