[Arran]

Good old 25 cycle transformer. Also since it has a single ended output, and uses mostly loctals with 150 ma filaments, it will not overstress either the 7Y4 or the transformer much. It's strange that they would use a 7B5 rather then a 6K6G or GT as opposed to the U.S built Tropic. I've noticed that the 6K6G and 6K6GT was an underutilized tube in Canadian built sets, most seemed to prefer using 6F6Gs unless it was a small table set, though Rogers seems to have liked 6K6Gs but they manufactured their own version that they called a 41M, with a metal spray shield, something unnecessary for a power output tube. Ironically Rogers was one company that went overboard when it came to what power transformers they used in a given model.
Regards
Arran