Just take the lid off the tank. This should reveal the linkage from the handle to the syphon. It may have just come adrift in which case it simply needs connecting back up. alternatively it might have corroded and broken. In this case one way round it that I have found is to use the metal hook off a plastic (or possibly wooden) coat hanger and bend this to the required shape. If, as you say, it's the handle that has broken you will need to get a new one, but you shouldn't need to remove the syphon.
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