How does one open an Adcom 750 preamp?

I intend to install Marigo dots in my 750 preamp, but I can't figure out how to open it. Please advise.
Had one years ago and it's Torx or hex keys on sides ,aybe nack where cover wrapsaround..But if you can't open why do so?High volatge you might damage something on board.Be carefull and use one handed rule (don't us second hand on ,near,or in anyway connected with unit)even if just vaccuming dust out.