It has saved two devices of mine from an early death. hk citation 16a hafler dh200 In the citation, I was removing the screen cover on the heatsink to take a reading from an emitter resistor with the amp on and hooked to the DBT. As I was removing the cover, I dropped in into the heatsink creating a short from an emitter resister to chassis ground. Light went BRIGHT and the amp is fine. What would have happened without the DBT? Who knows With the hafler, a solder blob fell onto the bridge diode shorting the transformer lead to chassis ground. Bulb went BRIGHT when I fired it up. The transformer would surely be toast had it not been for the bulb.