[Arran]

ARRAN: You and I both need to get our signals straight about which country certain tubes were used. I forget that tubes, such as 5Y4 were used in Canadian radios, by RCA. I think that there were others too, though examples escape me. Apparently, Canadian RCA wasn't as tightly under Sarnoff's heel as the US RCA. While a lot of Canadian RCA sets used he same chassis as those offered to the south, a great lot of them were totally designs that were Canadian RCA only. Quite a few of the Canadian RCA's were a lot better in quality of design than their similar sister sets in the USA.

So, having serviced radios since 1944, I have a clear idea about what went on south of Canada, buit the Canadian GE and RCA were different creatures.

As I said, I could only comment on the Canadian produced sets. What may explain the use of 5Y4s in Canadian RCAs, if it indeed is unique to Canada, is that in Canada we had company, a sort of patent pool, called Canadian Radio Patents limited that the manufacturers owned shares in and could purchase licenses to employ various circuits and devices in the radios that they produced. Rogers owned many of the patents for AC tubes and power supplies in Canada, RCA owned the Superheterodyne, Regenerative and TRF patents, and other companies like Northern Electric and Canadian Marconi held their own, CRP Ltd. allowed radios to hit the market years sooner through co-operation.
There is also the possibility(but a remote one) that the 5Y4 was preferred over the 5Y3 because the 5Y3 was not approved under the Canadian electrical code prior to the war. For example you won't find any Canadian made AC/DC sets built prior to 1939-40, the small sets prior to then were AC even if there was a similar set with an AC/DC circuit in the US .
Best Regards
Arran