Units are vacuum impregnated with polyurethane varnish for quiet and long life operation. Line output transformers with silicon iron C cores.
Photo 8 shows a medium-power C-core power transformer, a single-loop transformer with windings on both legs of the core. Specifications Part Number 2731380 Impedance 1kHz, 1V, 0mA DC Input 1 Kohms ± 10% DC Resistance (Input) 70 ohms ± 20% DC Resistance (O Location: Central Pa, 17044. 3 V filament test transformer, and clip one alligator clip to the output transformer secondary tap. Mouser offers inventory, pricing, & datasheets for Tube Output Single Ended Audio Transformers / Signal Transformers. Has anyone ever used a Bogen T725 transformer for a speaker in a tube circuit? Tube Output Single Ended Audio Transformers / Signal Transformers are available at Mouser Electronics. Before you can complete your amplifier you should choose the output tube that you want to use, and then choose an output transformer to match that tube. I would leave it unconnected and use the red (8 ohm) or brown (4 ohm) wires for feedback.
Tube radio output transformer The old one is toast.