Is this capacitor deformed? - Page 1
Forum section: electronics / projects

author: timb
author_rank: Super Contributor
timestamp: August 26, 2015, 02:48:43 am
content: I had to open my Tek DMM4020 to fix a broken clip inside the front panel. Looking at the main PCB, I noticed this capacitor. It appears deformed, but it's not leaking.Is that some weird shape I've never seen before? Does it contain a miniature black hole causing it to implode (and trapping the electrons in a singularly)? Or is it a dud?Sent from my Smartphone

author: rickselectricalprojects
author_rank: Regular Contributor
timestamp: August 26, 2015, 02:52:26 am
content: i have blown up so many electrolytics to know that the cans are not that shape so yes i would say it is deformed. (don't quote me on that though)i hope this helps

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 26, 2015, 02:52:48 am
content: If it's regular and even, that's normal for some types; crimping the sides allows more heat transfer. Although I've only seen it in big ones (computer grade sized).Tim

author: ataradov
author_rank: Super Contributor
timestamp: August 26, 2015, 04:08:56 am
content: That does not look regular at all. I'd say this one is dead.If you decide to replace it, do a teardown of this one. Never seen them implode, it usually goes the other way around

author: edpalmer42
author_rank: Super Contributor
timestamp: August 26, 2015, 04:21:20 am
content: Sometimes a plastic sleeve will ripple like that when it gets hot. It kinda wants to shrink, but it's not heat-shrink so it gets confused. Does that capacitor run hot?Ed

author: SeanB
author_rank: Super Contributor
timestamp: August 26, 2015, 04:33:31 am
content: Probably was crushed by a pick and place machine during assembly, leading to the crushed sides. Probably should be removed and replaced, though it probably is still working well. Have a look at DextersLab for a teardown of one of Ian's scratch and dent large caps.

author: ataradov
author_rank: Super Contributor
timestamp: August 26, 2015, 04:48:43 am
content: Quote from: SeanB on August 26, 2015, 04:33:31 amIt actually takes a lot of force to squeeze the capacitor like that. I doubt anything in a PnP machine can get even close to the force required.

author: calexanian
author_rank: Super Contributor
timestamp: August 26, 2015, 05:24:58 am
content: Defiantly a singularity in that one. Watch out for various radiation and other charged particles. My rule of thumb on caps is if anything about them catches your eye, just go ahead and change it. They are cheap. Far more so than any amount of time worrying about them.

author: Deathwish
author_rank: Unknown
timestamp: August 26, 2015, 05:41:19 am
content: Yes, I had one on one of my frequency Generators I have that looks like that, i had to remove it.

author: timb
author_rank: Super Contributor
timestamp: August 26, 2015, 07:44:58 am
content: Okay, I'll replace it. As far as I can tell, it isn't running hot (I'll run it with the cover off this afternoon and see how warm that area gets; there are a bunch of diode bridges and three linear rectifiers only being cooled by the PCB board). It's run fine over the two years I've owned it (and it came brand new from Tek).I kind of expected better QC from Fluke/Tek. Ah well, I guess I can clean the flux off the board too (in the analog section, no less, which is just shameful on a 5.5 digit meter).Here's a few bonus pictures to show the cap in relation to other parts:Sent from my Tablet

author: dr.diesel
author_rank: Super Contributor
timestamp: August 26, 2015, 11:17:55 am
content: I have a 4020 as well, dangit, now I gotta yank it apart and see what mine looks like, LOL.

author: dexters_lab
author_rank: Unknown
timestamp: August 26, 2015, 11:56:16 am
content: Quote from: timb on August 26, 2015, 02:48:43 amQuote from: SeanB on August 26, 2015, 04:33:31 amThe internal clearance will be much smaller on a low voltage capacitor so it could well have crushed the insides, probably best to change itthis is the 450v cap i did a teardown on:

author: dom0
author_rank: Super Contributor
timestamp: August 26, 2015, 12:09:45 pm
content: Some large caps just have these six "dents". I guess they mechanically support the winding. If they're regular around the cap I'd not care, but if they look very irregular it's probably not made by the cap factory and I'd replace it.

author: MagicSmoker
author_rank: Super Contributor
timestamp: August 26, 2015, 01:39:07 pm
content: I've seen this happen before when an elko overheats and the vent seals shut after releasing a little bit of the electrolyte. In any event, this is not normal.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: August 26, 2015, 02:19:40 pm
content: Like I said, bigger ones can be crimped around the sides for better heat transfer. They leave quite a bit of space inside them, sometimes, I guess.Dexters: your caps are fine. It's a feature, not a bug. Meanwhile, back to putting speed holes in my car...Tim

author: onlooker
author_rank: Frequent Contributor
timestamp: August 26, 2015, 02:58:50 pm
content: I guess the OP can better see if it is a machined shape or one caused by damage or it is just the plastic wrapper.

author: timb
author_rank: Super Contributor
timestamp: August 28, 2015, 08:08:56 am
content: Quote from: onlooker on August 26, 2015, 02:58:50 pmTurns out, it was just the plastic wrapper. I guess it didn't evenly shrink or something? The plastic was so rigid that it made it look and feel like the metal was dimpled. In fact, I didn't realize until after I had unsoldered the cap (at which point I removed the plastic).The can itself was a perfect cylinder and it tested fine, so I printed out a new label and soldered the cap back on the board.So, that explains that.Sent from my Tablet

author: printplaatreparatie.nl
author_rank: Contributor
timestamp: November 16, 2021, 03:57:20 pm
content: Very old topic, I know but didn't want to start a new one for my post.I found that some new capacitors are dented as well. I remember seeing the dents on big fat caps in old industrial equipment, but found dents in my new Vishay caps.At first I was puzzled, because the ones in stock were almost identical with no deformations. But then I noticed the different vent and checked the order. I had ordered thehigh vibrationtype, which apparently has dents. Makes sense, as the construction might be stiffened by the dents.