Sounds like you took a ZAP, from a static or nearby lightning event.http://www.alphadeltacom.com/pg11.htmlModel SEP Arc-Plug™ Static Electricity Protector is a special gas tube component designed to “bleed off” slow rising static electricity buildup of the kind generated by thunderstorms, high wind driven snow or sand or by a harmless looking cloudy day. These static charges have been measured to several thousand volts and can damage or destroy sensitive components in receiver or transceiver front end circuitry.
To remove the Model SEP Protector, simply remove the antenna connection hardware and remove the SEP which is installed in the cavity on the back of the Model DELTA-C Center Insulator. Reinstall the hardware in the same sequence as provided.
Replacements are ~ $15, and look like this: http://www.universal-radio.com/catalog/antsup/3497.jpg
When using the DELTA-C for high power transmitting it may be neccessary to remove the SEP Cartridge when VSWR exceeds 2:1.