A BSC621 should be a
LNBF, dual band - C & Ku. It requires 13 volts to it to select Vertical Polarity. And 18v to select horizontal. Don't think that receiver is compatible. Think it supplies 18 to 24v at all times for use with an LNB mounted to a feed horn. (typical Chaparral
Examples) The polarity is controlled by the servo on the feed horn. (Three small wires to it)
If you have need for a replacement C band LNB, an ESX 211 (or similar) is the way to go.