how do you crack (open) a Rainbow mono monitor?

As am I. I don't think I own any computers tht are older than I am, alas. My HP9100Bs are a couple of years younger than me. The Casio AL1000 is close, it's about the same age , but I don;t know wheter it was made before me or vice versa. I do have older mechancial calculators, but as they're not programmable, I don't class them as computers. I've certainly demonstrated some of my machines tp student audiences where the machine is older than everyboduy in the audience.... Hmm.. A turntable on plinth is about 2' by 18" I think. The pre-amp, well, it's only going to be 4 valves and no big rransformers, so that's quite small.. You must be even shorter of space than I. I was thinking that perhaps you meant an EMG accoustic gramophone with a 4' horn or similar, but then I notices the 'pre-amp'... -tony