Different OT on 1958, 1973, 1974?

[junior marbles]

I am unsure whether the original 1958 which has an output impedance of 8Ω (two 10s @16Ω in parallel) used the same identical OT as the 1974 which was driving a single 16Ω speaker, or the 1973 which, like the 1958, used 8Ω (2x12" @16Ω).

The schematic I could find online is unofficial/hand scribbled. I cannot find any authoritative information whether any of these OTs had taps for different loads to match the speaker loads of these three models.

[Graydon]

The original 18 watters used a Radiospares multi-wind output transformer. You can get all three typical impedance settings but it is slightly complicated to switch. It looks like this...

[junior marbles]

Thank you. Very informative.