Electrolytics blow after 1 hr

Only once? I think I've probably done it maybe 10 or more times in my life. Sometimes, nothing happens. Other times, I spray smoldering oily confetti all over the shop. Back in the tube days, I once managed to convert a metal can electrolytic into a small rocket, that cracked the Bakelite(?) case on the TV. With tantalums, the amount of toxic smog that such a small device can produce is truly impressive.

Of course, after discovering I had simultaneously missed the obvious and ruined my reputation for infallibility, I managed to make things worse. I had visitors in the office at the time, and was engaged in a very distracting conversation, while trying to replace the reversed electrolytics. Of course, I had solder in two caps backwards before I noticed that I had repeated my mistake. It's really hard to ignore the silk screened + sign, and the square pad on the + lead but I succeeded. Since it was obvious that nothing useful or successful was going to happen last night, I replaced the caps, ran a few simple tests, and made a hasty exit towards home.

In the true spirit of Learn By Destroying(tm), I measured the temperature of the various caps with a thermocouple probe. 36C on all

4 caps whether inserted backwards or correctly. Basically, the same temperature as most everything else in the area. It appears that these caps do NOT get unusually hot when reversed. Some do, but these didn't. Also, I'm rather impressed that the Dell PCB pads did not fall apart after having the same parts replaced ummm.... 4 times.

Nicely done. I vaguely recall cutting across a hot zip cord while plugged in, and destroying a pair of borrowed pliers. That was minor compared to all my other mistakes and accidents, which I'll mercifully decline to itemize.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

One of my first "I did this" projects was a small line powered phonograph amplifier built from the RCA Tube Manual book.

It's pretty impressive when you put the voltage doubler caps in backwards.

Lesson learned, "Electrolytic capacitors are fussy about polarity."

Or course later on, this came in hand when we used to shove a

250 uF 150 V "little beaver" into the end of a line cord and leave it in the trash can next to another tech's bench. Wait until they're deep in the middle of something and plug the cord in.

Great hilarity ensued.

Jeff The other other one.

Phil Allison Inscribed thus:

Good catch Phil :-)

--
Best Regards:
                          Baron.

Jeff Liebermann Inscribed thus:

I wouldn't beat yourself up about it... I'll bet we have all made some mistakes in our time. :-)

--
Best Regards:
                          Baron.

I once was trying to remove a photographer's external slave flash powerpack from it's case using two hemostats. I happened to clamp on the plus and minus output. I think it was 900 volts dc and had several large electrolytics about 3/4 the size of a soda can. Residual voltage caused my arms to fly outward and I stabbed a friend in the shoulder with one pair or the hemostats.

--
Live Fast, Die Young and Leave a Pretty Corpse

Ah, but we've all been there Jeff, we've all been there ... :-)

Arfa

In article , Jeff Liebermann writes

I did exactly that a few weeks ago in a moment of inattention. Fortunately, because we have a decent electrical wiring code here in the UK, all that happened was that the 3A fuse in the plug blew.

Over that side of the pond, the only protection you have is a 16A or 32A breaker in the cabinet, which explains the destroyed pliers.

--
Mike Tomlinson

In article , Smitty Two writes

Whatever.

The point still applies. You only have the cabinet breaker to protect the circuit, here we have individual fuses per plug in addition to whatever fuse(s) the connected equipment has.

--
Mike Tomlinson

In the USA, we only make big mistakes, so oversized breakers are totally functional. We also use it as a Darwinian filter, as sloppy techs usually don't survive very long. After 150 years of natural selection, we have bred a race of very careful technicians.

Circuit breakers here are in increments of 5A up to about 25A for domestic service. None of my breakers are labeled, so if I need to know which breaker controls which circuit, I just plug a short into the wall socket, and check which breaker has tripped. Very handy.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

All that proves is that you live in a 'nanny state'.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.

Meat Plow Inscribed thus:

Ouch !

--
Best Regards:
                          Baron.

In article , Michael A. Terrell writes

Actually, it proves that we have a well designed and well thought out premises wiring code which protects people and the appliances they use. And we can actually boil a kettle in a reasonable amount of time.

What are the figures for electrical fires in the USA again?

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Mike Tomlinson

310 deaths last year. About 1/3 of the electrical fires involve electrical shorts of some sort. Even with fuses in the power plugs, shorts in the walls will have the same effect in both systems:

...for 1993 - 1997 are that 41,200 home structure fires per year are attributed to ?electrical distribution.? These electrical distribution fires account for 336 civilian deaths, 1446 civilian injuries, and $643.9 million in direct property damage per year.

During a typical year, home electrical problems account for 28,600 fires and $1.1 billion in property losses. 53% of residential electrical fires involve electrical wiring.

I couldn't find any statistics for UK.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558

They are available online if you really care.

What are the figures for the UK?

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.

20,000/year electrical fires, etc. in the UK according to:

3,000/year in Ontario Canada (about thirteen million folks):

John :-#)#

--=20 (Please post followups or tech enquiries to the newsgroup) John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call (604)872-5757 or Fax 872-2010 (Pinballs, Jukes, Video Games)

"Old pinballers never die, they just flip out."

In article , Michael A. Terrell writes

Evasion of question noted.

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(\__/)   
(='.'=) 
(")_(")

Evasion? Numbers for both the US and UK were posted in this thread. From what I saw, the UK is a huge tnderbox of poorly wired buildings. Then, multiply the UK numbers by 5 to compare them to the US.

--
You can't fix stupid. You can't even put a Band-Aid? on it, because it's
Teflon coated.