Only when the silver solder melts [430ºF], runs out and the threaded header falls off. Doorknob caps typically fail from a short through the barium titanate dielectric. >Is it possible for a plate blocking capacitor to open? It's a door knob type >100 pf at 5kv in a vhf amplifier, centralab type. ... - R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, www.vcnet.com/measures. end