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Old 21st October 2012, 02:08 PM   #21
AndrewT is offline AndrewT  Scotland
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3mins gone and no-one posted "silly bugger".
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Old 21st October 2012, 02:11 PM   #22
Trout is offline Trout  United States
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Quote:
Originally Posted by AndrewT View Post
not filter caps but much more dangerous.

A.
Toasting a slice of white pan bread on a metal fork at the bars of an electric heater.


Touched something that made me tingle/jump ! I was quite young and over-worked Mum was not looking just at that moment.

B.
Volunteered as a 12 year old, to "repair" the damaged flexible cable where it entered the back of the cylinder vacuum cleaner.
Went and got a screwdriver.
Unplugged the socket from the Cleaner. Removed the cover and started to unscrew the wire terminals securing the three core cable. My "pinky" touched the Live while I was undoing one of the others. Jump !!!!! I had forgotten to unplug at the Mains end.

This one may be the reason I push Safety so much on this Forum.

pinky = little finger opposite the thumb (in the UK)

I have done that!!!
Broke the heater element and messed up the toast as well, I think that was the origin of the miracle toast people originally listed on ebay lol
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Old 21st October 2012, 02:17 PM   #23
AndrewT is offline AndrewT  Scotland
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I got a little 9Vac mains transformer. Wires inserted up the sleeves of my jacket, back to the transformer in my pocket.
In the other pocket was a D cell (1.5V).

I Sellotaped the inside of my hand and stuck the pair of leads from the 240Vac winding to that tape.
I had the other pair of wires in a series connection from my "spare" hand switch to the 1.5V battery to the 9Vac winding.

Have you guessed yet?

Offer to shake hands.
And watch them jump as I switched the D cell on and off.
I thought it was funny.
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Old 21st October 2012, 02:26 PM   #24
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I damn near lost my hearing just 3 days ago! I was powering up a new unit loaded with 470uf 450V caps. I had been at full voltage for a minute or so when I reached over to turn the radio up a bit which put my left ear...my good ear...within 18"-24" away from the unit when one of the caps blew BANG with the volume of a firecracker going off! couldn't hear anything for 2 days! I see an audiologist Monday to see if i did any permanent damage!
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Old 21st October 2012, 02:30 PM   #25
DUG is offline DUG  Canada
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Teenager learning electronics (tubes...back in THE DAY)

damp (concrete) basement

Aluminum chassis (tube) PS on the floor

370V from 300uF...made me jump a little.

I was learning
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Old 21st October 2012, 02:44 PM   #26
agdr is offline agdr  United States
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Back when I was a kid in college I was repairing a tube TV that had a 60Hz hum problem. Big console TV that had been unplugged and off for several minutes. I was lying on the floor with the metal chassis pried up, checking some resistances, when I got across a 200V+ power supply filter cap. Either the pop, or me yelling, or both, was loud enough that everyone in the shop came running. But that found the problem - a bleed resistor across the cap had opened up. Talk about using your body as test equipment.

Last edited by agdr; 21st October 2012 at 02:49 PM.
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Old 21st October 2012, 03:39 PM   #27
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Quote:
Originally Posted by Zero Cool View Post
I damn near lost my hearing just 3 days ago! I was powering up a new unit loaded with 470uf 450V caps. I had been at full voltage for a minute or so when I reached over to turn the radio up a bit which put my left ear...my good ear...within 18"-24" away from the unit when one of the caps blew BANG with the volume of a firecracker going off! couldn't hear anything for 2 days! I see an audiologist Monday to see if i did any permanent damage!

yea after seeing first hand what happens when you get polarity crossed wrong on them suckers just start running rofl
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Old 21st October 2012, 03:42 PM   #28
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what brand of caps were they? just some duds Im guessing?
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Old 21st October 2012, 03:47 PM   #29
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I got some old Panasonic/ELNA 47uf 450v and 100uf 450v they are old I'm afraid they might blow up man lol I would like to try em though especially the ELNA's heard they sound killer lol
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Old 21st October 2012, 06:43 PM   #30
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In 50+ years of playing with electricity there are bound to be a few incidents. I have had more than my share. The serious events were mostly when I was young, stupid, and invincible.

There have been some capacitor explosions. There is still some schrapnel embedded in my ceiling from a capacitor in a PC power supply that is fed by line voltage through a shorted bridge rectifier. Yes the big dumb blonde one jumped the fuse. Now I use a 100 watt light bulb.

More recently I had a 47uF 450V Nichicon explode so violently that I never found all of it. It was fed from a big old variable power supply that gets its stability with a 470 uF cap across the output, set on 600 volts. There was a 10K 1 Watt resistor in series with the cap. Why didn't the resistor just fail to an open when the cap shorted? It did, but then there was 600 volts across a resistor rated for 300 volts. A plasma ball erupted across the resistor allowing most of the energy in the power supply to be applied to the cap. After it was over there was a burnt spot on the PC board where the resistor was, and two short wires where the cap was.

Shocking events happened too. I have a large scar on my arm from a TV set in high school. It was 1969 and TV's had tubes. The CRT is the filter cap on the output of the HV rectifier. There is a conductive coating on the inside of the glass connected to the HV and a coating on the outside of the glass that is grounded. A screwdriver was usually slipped under the HV connector and arcced to ground to test for HV. Somehow the 25KV jumped to my finger instead of ground. My arm was sliced open by the convergence board while involuntarilly retreating from thr TV set.

The scarriest event happened in about 1976. A friend asked me to put a surplus Gates 5KW HF transmitter on the air. The transmitter required 3 phase power that was not available in his building. I informed him that he would need a big transformer that accepted 240 volts single phase and output 7 to 8 KV at 1.5 amps or more. He found a suitable surplus unit about the size of a small file cabinet. I wired it into 4 diodes of the original 6 diode bridge. I used a line contactor from an industrial AC unit to connect it to the line voltage. Whenever the TX was enabled the 60 amp breaker tripped violently. The romex running across the warehouse floor jumped several inches. Clearly there was a bad short somewhere. I immediately suspected the large filter cap since it had a large dent in its side. I got a trusty Simpson 260, set it to OHMS and proceeded to measure the cap. There was a very large BANG, about an inch was gone from the end of the red probe and the meter case was shattered. I decided to go home for day. The next day I brought a HV probe and found about 4KV left in the cap.

After discharging every cap in the power supply, I decided to measure every part in the power supply. Two of the six 50 watt bleeder resistors were open, and one of the six power supply diodes werte shorted. This allowed the filter capacitor to charge on one half cycle while the short on the other half cycle attempted to blow the breaker.

Looking back, I was about to disconect the suspect cap before deciding to ohm it.....It had large nuts holding the lugs, and I had a metal Crescent wrench.

Quote:
pinky = little finger opposite the thumb (in the UK)
pinky in UK = pinky in US
Crescent Wrench in US = adjustable spanner in UK
Monkey Wrench (Foo Fighters song) != Chimp Spanner (UK prog band)
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