Almost Got My Eye Poked Out

[josh132]

So you all know, when you connect an IC to the wrong voltage and put 10x more current its capable of, the IC blows up. Faulty ICs and mosfets can blow up. I was using an IRF530N n channel mosfet for some general switching, but as i rose the voltage, the mosfet blew up. the shrapnel hit the lower part of my eye leaving a black eye and a lot of pain. Moral of the story: always double check if you set your current limiting correctly. I had it set at 20 amp. On a faulty mosfet.

[Someone]

or you know... wear PPE when dealing with high energy systems.

[rstofer]

The real lesson is to always wear safety glasses.  Not that I expect many people to actually do that but when you are working with high energy, "oopsies" are always a possibility.

[jmelson]

Yup, years ago I was working on a 1 KW power factor corrector / inverter.  I had a problem with it blowing IGBTs.
I eventually started powering it up while crouched under the bench with ear protectors on, after having a pair of IGBTs simultaneously pass by both sides of my head by a few inches, glowing yellow!

Jon

[VK3DRB]

Tantalum caps that have been soldered in reverse can have a much more dramatic effect. I have seen in manufacturing on occasion, fireballs of white hot tantalum capacitor material fly off the board. In one case melting a deep hole in ESD flooring. After this, all PCBA ICT and functional test equipment required shields; and all debug technicians were required to wear safety goggles as a condition of their employment.

Who was the clown that came up with the hare-brained idea that the negative line marking (-) means positive on a tantalum capacitor? I see no common sense in this approach. The negative line means negative on everything else including electrolytic capacitors, schematics and in mathematics.

[SilverSolder]

[...]
Who was the clown that came up with the hare-brained idea that the negative line marking (-) means positive on a tantalum capacitor?
[...]

Sounds like whoever it was, went to a pretty good party the night before...

[rdl]

Those damn ICs are always causing trouble.

[james_s]

I've had shrapnel from power mosfets bounce off the ceiling on a couple of occasions, power electronics can be pretty exciting. These days I normally put a piece of lexan or something over parts that are likely to grenade when I'm testing.

[BrianHG]

When I was a kid, back in the late 70's.  I had a RadioShack 200 in 1 (I think...)  It had those 2SAxxx/2SCxxx style metal can transistors.  I don't know what I did, but one blew up.  Fired like a bullet.  I was looking for the case everywhere.  I finally discovered a hole in the ceiling right above me....

[PwrElectronics]

Had a near miss long ago.  Shortly before I needed to wear glasses I was working on something and a TO-92 package device blew and a chunk when whizzing past my head just past my eye.  Found the piece 1/2 way across the room behind me.

At a prior work place, I was a engineer at the factory responsible for some production testers.  We made power supplies.  There was this bare board assembly that was 90-240VAC to 48VDC that got tested separately before being installed in the chassis and final assembly.  The test fixture was a box with a clear plastic lid that the test operator put the board into and connected the cables and closed the lid (on a interlock switch).  This board had a bunch of electrolytic capacitors on it that were installed by hand on the line and wave soldered.  It was not uncommon for that to be done wrong with 1 or more of them in backwards.  Those caps were off of the line rectifier for a off-line switcher topology.  They would not blow right away but seemed to let go when the test sequence changed from the nominal 120VAC tests to the 240VAC tests.  Then they would vent violently and loudly.  That plastic lid had to get replaced with a sturdier material after it cracked from impacts and it was also melted.  There was a very "jumpy" young woman that usually ran that station and she soon learned to check those boards carefully for backwards caps before hitting the start button on the tester!

[coppercone2]

I wear safety glasses when dealing with any power PCB. capacitors can go off too.

[coppercone2]

Had a near miss long ago.  Shortly before I needed to wear glasses I was working on something and a TO-92 package device blew and a chunk when whizzing past my head just past my eye.  Found the piece 1/2 way across the room behind me.

At a prior work place, I was a engineer at the factory responsible for some production testers.  We made power supplies.  There was this bare board assembly that was 90-240VAC to 48VDC that got tested separately before being installed in the chassis and final assembly.  The test fixture was a box with a clear plastic lid that the test operator put the board into and connected the cables and closed the lid (on a interlock switch).  This board had a bunch of electrolytic capacitors on it that were installed by hand on the line and wave soldered.  It was not uncommon for that to be done wrong with 1 or more of them in backwards.  Those caps were off of the line rectifier for a off-line switcher topology.  They would not blow right away but seemed to let go when the test sequence changed from the nominal 120VAC tests to the 240VAC tests.  Then they would vent violently and loudly.  That plastic lid had to get replaced with a sturdier material after it cracked from impacts and it was also melted.  There was a very "jumpy" young woman that usually ran that station and she soon learned to check those boards carefully for backwards caps before hitting the start button on the tester!

might be wise for production to put sharpie marks on top of the capacitor (arrow) so you can see from the top if they are installed in the correct polarity, it might be worthwhile if you have enough power capacitors

You would think they would put a top side marker on capacitors that plainly visible because their expensive, fail bad, inserted manually, difficult to rework (goo). They treat it like a stupid 2 cent passive component but they are like $6 each for a good one. Like a red dot. Granted good capacitors are asymmetrical.