[RodB]

I wasn't able to locate the schematic for a 46-431 to get the audio output power. Your schematic might have the spec. So let's say it's about 5 watts. You can get a 5 watt universal OPT for a very reasonable price. Make sure the primary impedance matches the 6K6 at around 7.6k ohms (6k - 8k) and the secondary matches to the speaker voice coil impedance, probably 3-4 ohms. You may get lucky and find one that has the same mounting holes. There's a way to calculate your unknown OPT impedance but you may not have the equipment.