It’s dangerous to open up a CRT if you don’t know what you’re doing even if they’re not plugged in because they have giant capacitors (IIRC) that can still give you a fatal shock. I need to test some stuff in a 22" LCD monitor, and the casing reads HIGH VOLTAGE but I’m wondering if it’s unplugged if there’s any electrical hazard like there was with old CRTs.
In an LCD monitor, the HV is almost certainly related to the power supply for the illumination source, and there is no secondary storage of the energy. The inverter drivers for the backlighting system is normally a small switching supply that takes 5-12VDC in, and generates 3,000 to 12,000 volts, but again, only when on.
CRT sets weren’t dangerous because of capacitors, the charge there bled down quickly, but more so because the tube itself could a) hold the beam acceleration potential (typically about 1kv / diagonal inch of display) for a very long time and b) the deep vacuum in the CRT itself made them susceptible to implosion if the relatively weak glass on the rear side of the tube itself was damaged…
That’s just another way of saying that the tube itself was a capacitor.
a crt even if not designed to act as a capacitor does have capacitance.
also intentional capacitors in the set could be dangerous if the bleed off failed.
safe work required a number of discharges before proceeding.
I thought the capacitors in CRT power supplies had a tendency for dielectric absorption, so they tended to float at high voltage for a long time, even if they were momentarily shorted. This is certainly a problem in other high voltage capacitors.