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

I could counter that by saying that while you may well hvee designed things that used said CRT, and may have handled the CRTs for many years, this does not mean you know exactly how the CRTs themselves were designed, and whether they remain sade if you remvoe the front glass layer I don't beelvie DEC designed the CRT, they bought it in. I am nto even sure all came from one manufacturer, in which case it may well be that some CRRTs are safe without the outer glass, some are not. _I_ don't know, and I'd rather not be showered in glass fagments to find out. Interesting. I am suprised there are any differentces between the CRt other than the phosphor. Why was this? Did all colours of CRT come from the same manufacturer? It probably is safe to run the CRT without the outer glass sheet, and I am sure you know what you are doing. Now tha I can well believe :-). My experience of safety requirements is that there are often hoops you have to jump through for no good reason. How did the green CRTs get roudn this (or were monitors/terminals fitted with said CRTs simply not sold in such countries? I am perhaps too far the other way. My father spend much of his working life working with UHV systems (and to be fair, the forces on the envelopedon't really change that much as the vaccum gets harder...) and had a few things implode. He warned me to take great care... Been there, done that... It wasn't so bad on the valve sets with half wave rectificions, with a bit of care you could ensuee the chassis was connected to the neutral side of the mains [1] and thus be relatively safe. The later IC-based sets with bridge rectifiers were worse, whichever way round the plug was connected, the chassis was live. [1] A common way to do this was to use one of those neon tester screwdrivers which would light up if touched on a live chassis. If so, revese the mains conenctions. A _NOT FUNNY_ 'joke' was to convice the newbie that if he took his screwdriver apart and turned the neon round, it would then light on a dead chassis. (Of course it does no such thing, it still lights on a live one). The serivec information for the PSU in one of my Philips machines includes all the waveforms round the chopper circuit. This is a SMPSU with a mains bridge rectifier. The instructions for obvserving these waveforms tell you to use an isolating transformer, or if this is not available to disconenct the maisn warth wirew in the 'scope mains plug. Err, i have this slight objection to a 'scope with a live cabinet :-) Seems reasoanble :-) -tony