He probably got as much pleasure out of the sounds the key made as he did those few times when the key actually found its way into the slot.
主干是个原级比较结构as...as（原级比较状语从句）.
先看前一部分：He probably got as much pleasure out of the sounds the key made
成分依次是：主语+状语+谓语+定语+宾语+原因状语+定语从句.
后一部分：he did those few times when the key actually found its way into the slot.
成分依次是：主语+谓语+宾语+程度状语+时间状语从句
参考译文：他从钥匙声中得到的乐趣大概跟他偶尔把钥匙成功塞进插槽获得的乐趣一样多.