Technics PX9 - How do I get in?

[Telboy61]

Hi, I've just bought a PX9 to donate to a local church, but some of the keys are intermittent. I'm guessing they need a clean. I've seen a couple of videos about using a very soft pencil, but at the moment I can't even get inside the piano. There are 4 hinges on the back which suggest that the top lifts up, but the top is stuck fast. What am I missing?