https://www.ebay.com/itm/AVR-SX460-Stable-Automatic-Voltage-Volt-Regulator-Half-Replacement-For-Generator/383030962154 SX460 is a half-wave phase-controlled thyristor type automatic voltage (AVR) and froms part of the excitation system for a bruch-less generator. In addition to regulating the generator voltage, the AVR circuitry includes under-speed and sensing loss protection features. Excitation power is derived directly from the generator terminals. Postive voltage build up from residual leves is ensured by the use of efficient semiconductors in the power circuitry of the AVR