There is some kind of capacitor for the CRT that can shock you with high voltage and supposedly cause harm, but I'm doubtful of that since a lot of current would also have to be involved. Static electricity from rubbing your socks on a carpet is very high voltage but still not harmful.
I found this warning which is also applicable to the earlier all-in-one Macs.
I. Disassemble the Mac SE/30 Box
1. Caution and Warning
Before working inside the Macintosh SE/30, turn off the power and disconnect the AC power cord.
The SE/30 contains high voltage (1,500 Volts), a high-vacuum cathode ray tube (CRT) and sensitive electronic parts.
To prevent serious injury, the first thing you have to do is to discharge the CRT. Discharging the CRT before working on it lessens the chance of an electric shock.
Some later compact Macs containing CRTs have a bleeder resistor on the anode that drains the charge when the power is turned off. However, if the resistor fails, the anode may retain a charge. Thus, you must perform the discharge procedure.
Never touch the anode connector or the anode aperture, that can regain some charge even after it has been discharged.
Secondly, you must be careful not to break the fragile CRT neck. Do not pick up or handle a CRT by its neck, where the tube is the thinnest. To prevent an implosion, take every precaution against breaking the CRT. Wearing safety goggles is preferred when working with a CRT. The CRT contains a high vacuum. If cracked or broken, the CRT can implode (collapse into itself) and scatter fragments of glass.
Thirdly, precautions are required not to break IC and LSI chips on the board by electrostatic damages.
Go ahead at your own risk. Nobody can take responsibility for you.
