[MrFixr55]

From the schematic, I think that the 2 6Y6s in this set are in parallel, not push-pull. Look at the output transformer. there are only 2 leads. The plates connect to the transformer through resistors. The grids of both 6Y6s connect to the plate of the 1st AF tube through caps. I have not seen many radios that se this tube. Id develops rather high power at rather low voltage and rather low impedance.

The 6Y6 has a very low load resistance (2600 Ohms). 2 of these in parallel have a load resistance of 1300 Ohms. Plate dissipation at 200V is 12W and max output at 200V is 6.5W for one tube. This is 6L6 territory. These tubes run at lower plate voltage than 6L6 or 6V6 but much higher current. IMHO, the 5U4 is justified, and plate dissipation of 24W in Class A (and remember, that even at idle, there is high plate current in Class A), the 5U4 is justified.