In their descriptive texts you will find a lot of mentions of 魚雷｛ぎょらい｝. However, it seems that they (北上 and related ships) are a different type of torpedo cruiser, since a torpedo cruiser generally gets called 水雷巡洋艦｛すいらいじゅんようかん｝. The Wikipedia text on 重雷装艦｛じゅうらいそうかん｝ seems to indicate these were remodelled torpedo cruisers into light torpedo cruisers. Did I understand that correctly?
But that still leaves the question open: is 雷装 a synonym for 魚雷, maybe in a similar style how 魚雷 took over from 魚形水雷｛ぎょけいすいらい｝?
Any additional hints or explanations about etymology very much appreciated.