3 ms·

Many PSUs do have bleed resistors, but plenty (especially cheaper ones) will not. More importantly, a damaged PSU may have a non-working bleeder circuit, and yo

Many PSUs do have bleed resistors, but plenty (especially cheaper ones) will not. More importantly, a damaged PSU may have a non-working bleeder circuit, and you'll only know when you discharge a cap. Hopefully across a resistor, rather than a screwdriver, and very much hopefully not an open wound on your skin. A CRT stores energy because it acts a a large capacitor. Some better monitors (especially late '90s open cage arcade monitors) had bleed resistors on the anode of the CRT to make servicing safer. It's not actually a ton of energy; the voltage is very high, but that's about it. A charged, unpowered tube will sting, but it's seldom a killer. The flyback transformer will give a potentially lethal shock, though. The anode cap has the thick insulation and is surrounded by aduadag for a reason!

i336_ 10y ago
I wasn't aware that "plenty" of supplies lack bleeder resistors - and ouch, I didn't consider the case where the unit might be damaged, thanks. Considering the level of energy stored in the average PSU cap, if I use a decent 5W or 10W resistor, should I hold it in a pair of pliers so I don't get burnt? (I'm guessing I'd definitely need to do that if I use a tiny 1W or 2W.) Also, as someone whose knowledge of electronics is very poor - is a resistor the best thing to use in this instance? And it makes a lot of sense to put bleed resistors on open cage CRTs - those types of units are unlikely to frequently power down/back up, so completely discharging the unit isn't an issue. Design win! I've heard stories about service techs getting bitten by the 70kV HV while testing tubes that were powered up for testing...