Worst injury I ever got electrically was the fall off the ladder. I never actually came in contact with the live wire - the cutties were insulated, but it resulted in enough force to knock me off balance. Not enough to make me quit work for the day or go to the ER, but was hobbling around the rest of the afternoon. I was about ready to kill the son of a b that wired the building. I had every breaker that serviced that floor off.
The worst shock was from a 20 V DC circuit. Interrupted, with a 50 amp inductive load. Felt like getting kicked in the chest by a horse - and I know what that feels like.
I had a pretty good zap from from holding up an 8 foot fluorescent tube under 345kV lines. When it was cold and damp and the lines were “sizzlin’ like a snare”. See, the higher you hold it, the brighter it gets. EEEEYOWCH! Getting 60 hertzed off 120 never bothered me after those incidents. Yeah, not pleasant, but not the end of the world either.
The worst shock was from a 20 V DC circuit. Interrupted, with a 50 amp inductive load. Felt like getting kicked in the chest by a horse - and I know what that feels like.
I had a pretty good zap from from holding up an 8 foot fluorescent tube under 345kV lines. When it was cold and damp and the lines were “sizzlin’ like a snare”. See, the higher you hold it, the brighter it gets. EEEEYOWCH! Getting 60 hertzed off 120 never bothered me after those incidents. Yeah, not pleasant, but not the end of the world either.
I do recall spending a good bit of time staring and marveling at my grandfather’s Fischer receiver at one point.
Also remember having noticed how certain products had a live chassis, a real eye opener for sure.(wtf!?)
Also remember having noticed how certain products had a live chassis, a real eye opener for sure.(wtf!?)
My lecturer told our class this way back in 1974:
Joe (don't know if that was his real name, but let's assume it was for now) was sent to the main railway station in Durban where I lived and grew up. This is a large railway station (if you are from the UK, think Waterloo or Kings Cross size) with an extensive PA system running off one of those high impedance line systems where you step the signal voltage up to a few hundred volts peak to peak but at very low current to send it all around the station, and then step it down with a local impedance matching transformer to drive an 8 or 16 ohm horn speaker. Joe was up a ladder and didn't have a pair of side cutters to hand to strip the wires to connect them to the transformer, so he used his teeth. As he was doing so, someone made an announcement. Of course, he lived to tell the tale, but never forgot his side cutters again.
Joe (don't know if that was his real name, but let's assume it was for now) was sent to the main railway station in Durban where I lived and grew up. This is a large railway station (if you are from the UK, think Waterloo or Kings Cross size) with an extensive PA system running off one of those high impedance line systems where you step the signal voltage up to a few hundred volts peak to peak but at very low current to send it all around the station, and then step it down with a local impedance matching transformer to drive an 8 or 16 ohm horn speaker. Joe was up a ladder and didn't have a pair of side cutters to hand to strip the wires to connect them to the transformer, so he used his teeth. As he was doing so, someone made an announcement. Of course, he lived to tell the tale, but never forgot his side cutters again.
The 1954 Philco TV my mother bought to watch The Guiding Light soap opera had a hot chassis. In WVa, no problem. In 100% humidity Houston where we moved 1956, if the plug was upside down the metal case would give me a good tingle if I touched it. Insulation chassis to case was cardboard! Where were wide blade plugs in 1954? It was still working 1976 when the wife traded it to a guy so he would mow the lawn.
Worse shock I ever experienced was 400 vdc off a 60 uf capacitor in a Ford car radio. The 1959 Ford car shop manual said the highest voltage in the radio was 12 v, but the dealership had installed a 1956 radio in the 1959 car with a 6 v dropping resistor. @#$)(* Ground was through my thumb, so no electrons crossed my heart. Ford achieved the 400 VDC with a thermal vibrator, which went defective in all three of the cars my parents owned. 1950 Chevrolet, 1954 Buick Super, 1959 Ford Ranch Wagon. Before internet, I had to carry the radio on my bike to my chemistry teacher's home to find out about vibrators. RCA Radiotron handbook at the the library had been zero help.
Worse shock I ever experienced was 400 vdc off a 60 uf capacitor in a Ford car radio. The 1959 Ford car shop manual said the highest voltage in the radio was 12 v, but the dealership had installed a 1956 radio in the 1959 car with a 6 v dropping resistor. @#$)(* Ground was through my thumb, so no electrons crossed my heart. Ford achieved the 400 VDC with a thermal vibrator, which went defective in all three of the cars my parents owned. 1950 Chevrolet, 1954 Buick Super, 1959 Ford Ranch Wagon. Before internet, I had to carry the radio on my bike to my chemistry teacher's home to find out about vibrators. RCA Radiotron handbook at the the library had been zero help.
Last edited:
I had two 50C5 stereo tube amps and a transistor table radio that were all hot chassis back in the early days. The better one of those two amps (the one with tone controls and 3 watts instead of 1) got “safetified”. The good Fisher receiver was not, but ultimately what did it in was a blown power trafo. The Philips ECG 7868’s all red plated and the transformer went smoke. It ran hotter than the blazes of Hell and Damnation normally, and I guess a few hundred mA more was a bridge too far.
Bonsai, I came across a older thread of yours on wiring a dual mono amp where you mention that building equipment with reinforced insulation is impossible for DIYers. Curious as to why? I would argue that reinforced insulation should be the goal, but adding a Safety Earth connection is a wise precaution for DIY built equipment that will not be hipotted. Or is that your reasoning: that DIYers will not have access to a hipot?
The "dual mono" thing brings up an idea I've had lately, only partly safety related. I've never liked the idea of having two (or more) power supplies in one chassis, as it doubles the chance of the primary-to-secondary isolation breaking down (admittedly low to begin with, but still). It's often 'necessary' to use several supplies as DC-coupled power amplifiers need both positive and negative supplies, and there are very few switching supplies with two outputs of equal voltage and power ratings (whether totally isolated or connected at the + and - outputs).
My idea is to have FOUR isolated outputs (whether a 50/60Hz transformer with four identical secondaries to go to four bridges/capacitor banks, or four DC outputs on a SMPS). These could power two isolated power amplifiers and the only connection between them would be back at the preamp output. This would remove a ground loop and the possible hum and noise it picks up.
My idea is to have FOUR isolated outputs (whether a 50/60Hz transformer with four identical secondaries to go to four bridges/capacitor banks, or four DC outputs on a SMPS). These could power two isolated power amplifiers and the only connection between them would be back at the preamp output. This would remove a ground loop and the possible hum and noise it picks up.
You can always try, but I just would not risk it. You or I may have enough confidence to do that, but what if I publish an article and tell someone how to build a double-insulated amp and they screw it up? With conventional earthed/safety grounded gear, they have to get one wire - the safety ground wire - bolted to the chassis good and proper and you know there's a reasonable chance if something goes wrong, they are at least protected. As I like to say, the most important connection in any DIY amplifier is the safety ground.
🙂
Thank you for the explanation. That the Safety Earth connection is the most important wire for a DIYer is wise counsel.
Last edited:
Not when you live in an old house in the Netherlands (or use unbalanced connections and don't like hum).
We have residual current devices. Those are obligatory even in old houses (although they weren't during most of my life).
I read that a few countries, such as Norway, use the IT system.
https://axis-india.com/tt-it-tn-earthing-systems/
https://axis-india.com/tt-it-tn-earthing-systems/
The box holds a new Asus Prime motherboard intended for use by someone intelligent enough to build or repair modern PCs. You would think that they shouldn't have to remind us that we shouldn't eat the CMOS backup battery!
Attachments
It costs $10 to recycle a LIIon battery in my county. Plus you have to go to the county center 11 miles from my house between 9 and 3 MTTF, 12 to 7 Wed. No, there is not a drop box anymore at HD.