Stay alert, this stuff'll get ya!

[AC_FX]

Here's a cautionary tale for tinkerers.  This is a picture of Brad, who was working on a negative-bias amp yesterday.  He replaced a big electrolytic cap and got the polarity backwards because he forgot he was working on a negative-bias amp.  When he put 390VDC to that cap, one end of it blew out, propelling the can like a bullet off the circuit board and into his midsection.  From the guitar side of the shop, we heard "BANG!" followed by "Uuuuuurrrrgghh" as Brad fell off his stool.  Fortunately it just bruised him up.

Obviously with the pedal stuff, we are working with much smaller caps and much lower voltages.  But they can still pop, and nobody wants to find out what it's like to take the exploded contents of one in the eye.  Stay alert!!

[Luke51411]

Ouch! Looks like a paintball welt.

[nocentelli]

+1
I once put a large 100uF backwards across the 9 volt rails on my breadboard, leaned across to swap a part, and moved my face away just seconds before it blew with a puff of acrid smoke and a fine spray of red hot liquid electrolyte.

[tabbycat]

nocentelli wrote

+1
I once put a large 100uF backwards across the 9 volt rails on my breadboard, leaned across to swap a part, and moved my face away just seconds before it blew with a puff of acrid smoke and a fine spray of red hot liquid electrolyte.

damn it, i thought as long as i stayed away from amp voltages i'd be safe. exploding caps at 9v?

now i'm worried.

[nocentelli]

Just put them in the right way around, and you'll be fine.

[tabbycat]

nocentelli wrote

Just put them in the right way around, and you'll be fine.

haha, just build an ocean liner fitted with enough lifeboats that is iceberg proof...

[Muadzin]

tabbycat wrote

nocentelli wrote

Just put them in the right way around, and you'll be fine.

haha, just build an ocean liner fitted with enough lifeboats that is iceberg proof...

Not going near icebergs also helps a lot.

[tabbycat]

Muadzin wrote

tabbycat wrote

nocentelli wrote

Just put them in the right way around, and you'll be fine.

haha, just build an ocean liner fitted with enough lifeboats that is iceberg proof...

Not going near icebergs also helps a lot.

stop victim-blaming.

[motterpaul]

I was working on a vintage amp yesterday and I have heard and read the warnings enough time to know to take care. I have never changed out a larger cap, though.

They say two things - play guitar while you turn off the amp, and if you hear the sound die away you know the caps are discharged - NOW, I DO NOT KNOW  if that is correct, I just heard it.

I also heard "always keep one hand in a pocket so you don't create a circuit where the current goes through your heart."

I have to admit, though, I have never heard of "shooting capacitors." That is a good one to know. Not that I have ever wired in a cap backwards in my life, though.  

[Beaker]

The electronics lecturer at the college where I work demonstrates the exploding electro cap on new students every year. Just touches the legs to a 9V battery terminals. Works every time - makes them pay attention and concentrate! It's worth doing  to satisfy your own curiosity - just do it outdoors and wear safety glasses.

[tabbycat]

Beaker wrote

The electronics lecturer at the college where I work demonstrates the exploding electro cap on new students every year. Just touches the legs to a 9V battery terminals. Works every time - makes them pay attention and concentrate! It's worth doing  to satisfy your own curiosity - just do it outdoors and wear safety glasses.

that is a lecturer who must love their paperwork. fe is risk-assessment hell these days. the wasted hours...

[GarrettVD]

Ouch… I got scorched by a little 3V3 zener diode (sans current-limiting resistor, oops…) among other things, but that is some next-level war wound he got!  Brad should stick to the bar-fight story, though, sounds cooler than getting shot by a capacitor  Hope he is fully recovered now!