Rca type 901769-501, 500 watt modulation transformer. The primary is center-tapped for push-pull modulators. The tranformer has two secondaries. Secondary #2 will carry 80 mils to modulate screens of beam power tubes or screen grid tubes. It is equipped with adjustable protective spark gaps on both primary and secondary. Primary will match any class b tubes up to 10,000 ohms plate-to-plate such as 810′s, 75t’s, 805′s, 8005′s, zb120′s, 203′s, hy51z’s, 211′s, 813′s, 828′s, 203z’s, etc. Maximum audio power: 550 watts. Secondary #1: 450 ma. Secondary #2: 80 ma. Pri to sec #1: 1:1. Pri to sec #2: 5:1. Pri to sec #2 tap 25:1. Pri to sec #2: 25:1. Pri to sec #2 tap: 625:1. Sec #2: 99 ohms. #2: 2000v to the rest of the coils and the core. Dimensions 9″ wide, 7 ” deep, 7 high. Mounting centers: 5″ x 8 “, with heavy channel iron mounting brackets. I strive to accurately describe all items. Please notify me immediately of any discrepancies. International: i will not falsify customs records. Exact amount will always be declared. Please be sure you are aware of the costs. The free listing tool.The item “RCA 500W Modulation Transformer (Vintage 500 Watt) Amateur Vacuum Tube Ham Radio” is in sale since Monday, December 01, 2014. This item is in the category “Consumer Electronics\Vintage Electronics\Vintage Audio & Video\Vintage Amplifiers & Tube Amps”. The seller is “cliffhiker” and is located in Lynchburg, Virginia. This item can be shipped worldwide.