Exploding cap in the face! - Page 1
Forum section: electronics / general

author: itdontgo
author_rank: Regular Contributor
timestamp: July 31, 2012, 08:23:39 am
content: Look what ended up in the 470uF 35V parts bin. Nice. It blew up right when my face was over the board the little b*stard!

author: digsys
author_rank: Unknown
timestamp: July 31, 2012, 09:09:51 am
content: Any idea why? Over-voltage? Ripple? They don't usually go for no reason, and it's looks like a good make.Injured? In my younger days we'd explode dozens for fun, even set friends up. Tantalum's are the BEST !!I still demonstrate the effects whenever I can, PURELY for educational reasons of course !!

author: rowant
author_rank: Contributor
timestamp: July 31, 2012, 09:11:53 am
content: Lucky you didn't lose an eye!You'll never blindly solder on a part without first checking you grabbed what you thought you did again! I did something similar many years ago, scared the shit out of me and I was standing away from it! Now I always check cap voltages and polarity every time I use one.

author: David_AVD
author_rank: Super Contributor
timestamp: July 31, 2012, 09:34:30 am
content: Quote from: digsys on July 31, 2012, 09:09:51 amI'm guessing more than 6.3V on a 6.3V rated capacitor. (intended capacitor was 35V rated he says)

author: DavidJRobertson
author_rank: Regular Contributor
timestamp: July 31, 2012, 09:42:04 am
content: I was once given anoldbench power supply. I plugged it in to test it out and it was outputting something like 37V when its intended maximum was 15V...A minute or so later, "BANG!", and smoke (+ a horrible stench) poured out of the vent holes in the power supply casing.The postmortem revealed that a large electrolytic cap had exploded - it was so old it wasn't vented. The metal can had flown off and a trail of electrolyte-soaked, twisted paper was ejected from the thing. At least it was an insight in to the construction of the things!David

author: Gall
author_rank: Frequent Contributor
timestamp: July 31, 2012, 10:50:07 am
content: I once exploded an 4700 uF 63 V large cap by soldering the rectifier backwards. It exploded AFTER the fuse was blown, about ten seconds later.I've also heard about some kind of cottage burglar alarm made from an old USSR-made K50-6 capacitor, something like a 10 uF 16 V. These capacitors had no protection notches nor any valve so they exploded like a pistol cartridge if connected to mains.

author: itdontgo
author_rank: Regular Contributor
timestamp: July 31, 2012, 01:32:41 pm
content: Yep 6.3v cap with about 20v over it. I got a wet face (and almost wet pants)! Is that stuff poisonous? Are the fumes poisonous?

author: nanofrog
author_rank: Super Contributor
timestamp: July 31, 2012, 03:44:19 pm
content: Quote from: itdontgo on July 31, 2012, 01:32:41 pmIt appears to be an aluminum electrolytic, so it's likely water based. But it could have ethylene glycol or dipropyl ketone, both of which are toxic if ingested (dipropyl ketone is also moderately toxic if inhaled).For a single exposure, I wouldn't panic (issues come from chronic/long term or very high concentrations of exposure). Just rinse off with plenty of water (presumes you didn't swallow any), including an eye wash if needed.

author: Dawn
author_rank: Regular Contributor
timestamp: July 31, 2012, 10:46:52 pm
content: Back in the 70's, a lot of communications gear used tantlums for non-timing critical applications. It wasn't that uncommon to power up a set that's been lying dormant for a while and one to smoke. Problem was that occasionally one would blow while you were working on the board and get that molten solder-like stuff on your hand. I still have several scars on the back of my hand and wrist from those eruptions.BTW, I got arrested for possession of tantlums in college. No kidding.

author: T4P
author_rank: Super Contributor
timestamp: August 01, 2012, 01:07:03 am
content: Ahh ... only to power a board packed with tantalums and watching it burst into flames ...

author: vk6zgo
author_rank: Super Contributor
timestamp: August 01, 2012, 02:57:18 am
content: Yes,back in the'70s,tantalums were regarded as the "silver bullet" for all types of situations,as they were so compact,& looked much more "high tech" than scabby old electrolytics!I began to think they had feet of clay,when quite a few which were in circuits where they were exposed to relatively high dv/dt ratios.started turning up brown !We had one place where they were used as bypasses replacing ordinary electros in parallel with a couple of micas on both sides of a directly heated filament circuit in an AM transmitter.Nice cooked tants,& we had to dig around in the odds-n-sods to find a couple of scabby old electros to get the thing going again.( out in the middle of the bush)We made the mistake once of using one for timing in a tone decoder which needed to operate when it saw TV field rate signals.This was so the Studio could turn Transmitters across the state on or off,by simply including or removing field syncs from the signal being distributed on the "Broadband" network.All was well for a while,then we started getting "no start" on one station.(Again ,out in the middle of nowhere.)The tant had permanently drifted in value.Out with the tant,in with a huge Polyester? (Anyway,we called them "greencaps".)No more problems.

author: labnet
author_rank: Contributor
timestamp: August 02, 2012, 04:16:40 am
content: In the 80's I used to wire up electros direct to 240v. A very satisfying gunshot sound.

author: T4P
author_rank: Super Contributor
timestamp: August 02, 2012, 08:24:58 am
content: Quote from: labnet on August 02, 2012, 04:16:40 amAC RICOCHET!