Capacitor broke off. :(


20 posts
by jbfink » Wed Apr 18, 2012 5:24 pm
Hey folks,

Just got my raspberry pi about ten minutes ago here in Canada, and while everything worked when I plugged it in and ran Debian off my SD card, when I unplugged it from power the small capacitor (attached next to the micro USB power, labeled "C2 C3 C6" on the board), which was just barely soldered in in the first place just upped and broke off. Luckily the power was off so I'm assuming the board is otherwise OK. I was able to retain the cap (but not the black base it was attached to).

Has this happened to anyone else? I suppose if something *has* to break on the board the little capacitor is probably one of the better ones -- I've done some (through-hole) soldering and have access to people who are surface mount soldering wizards, so if it's something that can be fixed locally I can probably swing it. Or if the capacitor isn't *strictly* necessary I'd like to know that too. :) Thanks.
Posts: 2
Joined: Wed Apr 18, 2012 4:13 pm
by dom » Wed Apr 18, 2012 5:34 pm
I've broke mine off a few months ago. It's easy to use it as a lever point when pulling out the (often quite stiff) power cable.

The good news is I've suffered no ill effects from not having it.

Gert's view was that the capacitor is not enough to fix a bad power supply, and is not needed with a good power supply, so there's a very small window of it being necessary.

Don't worry about it, as long as power supply is okay you'll be fine.
Moderator
Moderator
Posts: 3864
Joined: Wed Aug 17, 2011 7:41 pm
Location: Cambridge
by jbfink » Wed Apr 18, 2012 5:37 pm
Pheeeoooo! Thanks so much, dom. I feel a lot better now.
Posts: 2
Joined: Wed Apr 18, 2012 4:13 pm
by Lob0426 » Wed Apr 18, 2012 9:07 pm
Are there any more components that we can just break off and it will still work? lol

Another component to remove to save money!
Back-powered 256MB as WordPress Server
Motorola Lapdock with 512MB
Modded Rev 1.0 with pin headers at USB

http://rich1.dyndns.tv/
(RS)Allied ships old stock to reward its Customers for long wait!
User avatar
Posts: 1868
Joined: Fri Aug 05, 2011 4:30 pm
Location: Susanville CA.
by Gert van Loo » Wed Apr 18, 2012 9:32 pm
dom said:

...
Gert's view was that the capacitor is not enough to fix a bad power supply, and is not needed with a good power supply, so there's a very small window of it being necessary.

..


It has always been good design practice to put a big capacitor just where your power comes in. These things are dirt cheap and it does not hurt. (Sort of better safe then sorry).Nowadays with the high frequency switch mode supplies they are less needed.
User avatar
Moderator
Moderator
Posts: 1843
Joined: Tue Aug 02, 2011 7:27 am
by bobc » Wed Apr 18, 2012 10:37 pm
This is why computers are normally put in boxes. And bare boards never given to kids ;)
Posts: 87
Joined: Fri Apr 06, 2012 8:01 am
by Michael » Sat Apr 21, 2012 9:39 am
To keep the design robust, would it be worth asking the factory to put a blob of glue over that component to help protect it a bit?  Or maybe no-fit it as others have suggested.
Posts: 341
Joined: Sat Jul 30, 2011 6:05 pm
by mahjongg » Sat Apr 21, 2012 4:04 pm
I'm guessing its a "Top-Hat" model, (round aluminium cylinder with a plastic base), perhaps in a redesign you could replace it with a "moulded epoxy" model which are mechanically much sturdier. Top-hat elco's are notorious for breaking of the boards.
User avatar
Moderator
Moderator
Posts: 4506
Joined: Sun Mar 11, 2012 12:19 am
by mahjongg » Sat Apr 21, 2012 4:07 pm
By the way, its C6, C2 and C3 are the much smaller ceramic 1nF and 100nF capacitors in parallel with C6 (which is 220uF) .
User avatar
Moderator
Moderator
Posts: 4506
Joined: Sun Mar 11, 2012 12:19 am
by liz » Sat Apr 21, 2012 5:37 pm
Michael said:


To keep the design robust, would it be worth asking the factory to put a blob of glue over that component to help protect it a bit?  Or maybe no-fit it as others have suggested.


Later ones will be through-hole mounted - we've noticed that there seems to be a temptation to put your thumb on it to use as a lever when you take the power cable out.
User avatar
Foundation
Foundation
Posts: 3901
Joined: Thu Jul 28, 2011 7:22 pm
by Michael » Sat Apr 21, 2012 6:23 pm
Yay!
Posts: 341
Joined: Sat Jul 30, 2011 6:05 pm
by linker3000 » Sat Apr 21, 2012 7:51 pm
liz said:


Later ones will be through-hole mounted - we've noticed that there seems to be a temptation to put your thumb on it to use as a lever when you take the power cable out.


Ah - beat me to the suggestion. Any chance the value will be higher too - say 470uF or 680uF to help with DC stability?
Posts: 62
Joined: Thu Mar 08, 2012 1:41 pm
by rew » Sun Apr 22, 2012 7:52 am
You guys seem to be able to get VERY small form factor big capacitors. Say 4* or 5* 47uF tantalum should be a lot smaller and electrically equivalent.

This capacitor would provide about 0.3 miliseconds of power should your powersupply suddenly stop.
Check out our raspberry pi addons: http://www.bitwizard.nl/catalog/
User avatar
Posts: 391
Joined: Fri Aug 26, 2011 3:25 pm
by Montala » Sun Apr 22, 2012 8:11 am
liz said:


Later ones will be through-hole mounted - we've noticed that there seems to be a temptation to put your thumb on it to use as a lever when you take the power cable out.


Thanks Liz, I do seem to remember that being mentioned before though, and was under the impression that the 'modification' had already been implemented.

By 'later ones', do you mean those which are being manufactured now, or further on down the line, as it were, as this does almost seem like an essential requirement?
User avatar
Posts: 638
Joined: Mon Mar 05, 2012 11:54 pm
Location: Herefordshire (U.K.)
by BertM » Mon Apr 23, 2012 12:49 am
I am afraid that a through-hole mounted capacitor may even be more fragile, as a small amount of space between the base of the capacitor and the board may make the capacitor behave like a lever with respect to its pins, pulling the out effectively when the capacitor is bent.

Adding a blob of epoxy glue might be cheaper than replacing the capacitors with tantalum equivalents, and the failure mode of regular electrolytic capacitors is a bit more graceful as well.
Posts: 30
Joined: Wed Feb 08, 2012 4:12 pm
by johnbeetem » Mon Apr 23, 2012 9:32 pm
This problem should go away once RasPi cases are available, so I wouldn't do any redesign unless the new capacitor is cheaper.
User avatar
Posts: 938
Joined: Mon Oct 17, 2011 11:18 pm
Location: The Coast
by linker3000 » Wed May 02, 2012 8:56 pm
Just for the record mine's come off too. I was extremely careful never to put any pressure on it and just picked up my board today and noticed that the capacitor was slightly raised on one side and then found one lead had fractured at the body of the capacitor, so it wasn't a solder joint that failed.

From previous comments it looks like the problem with these caps is being addressed but I'll think I'll see if I can find a suitable 470-680uF replacement at work - fortunately it's an electronics engineering company and we have tons of scrap/prototype boards to scavenge!
Posts: 62
Joined: Thu Mar 08, 2012 1:41 pm
by Quicky » Fri Mar 15, 2013 6:40 pm
Mine broke off as well but does not function :x !
I was able to solder it on, and get it working just for it to break off a few days later.
Now its impossible to reattach.
I've been scouring the internet trying to find a replacement with little to no luck,
I've found a large amount of components on www.mouser.com/ but couldn't find an appropriate match.
Can anyone find a capacitor I can replace it with?
Thanks a bunch
Posts: 8
Joined: Wed Mar 06, 2013 12:23 am
by mahjongg » Fri Mar 15, 2013 6:58 pm
The capacitor is nothing special, and its absence is very unlikely the reason your PI doesn't work.

These kinds of caps are made by many manufacturers and are known as "top hat elco's".
But you can use any radial elco just as well, if you must.

Here is a link to a datasheet of a suitable type from Farnells site: http://www.farnell.com/datasheets/1521266.pdf
and here a starter for digi-key http://www.digikey.nl/scripts/dksearch/dksus.dll?FV=fff40002%2Cfff80009%2Cfffc000a&vendor=0&mnonly=0&newproducts=0&ptm=0&fid=0&quantity=0&PV16=11814
User avatar
Moderator
Moderator
Posts: 4506
Joined: Sun Mar 11, 2012 12:19 am
by Bashster » Fri Mar 15, 2013 11:45 pm
Someone said earlier in the thread that if your psu is good enough you don't have to worry about this cap. That's not true, unfortunately. However, your Pi may work well enough without it unless the lead length between the Pi and the PSU is unusually long. Missing this cap may cause instability issues with the Pi similar to running buggy code. If this happens and there's no way to re-attach the cap, the you can try cutting the power lead's length down to an absolute minimum and see if that fixes the problem. Alternatively, feed power in via the GPIO pins and place a cap across the relevant two pins as close to the board as possible.
Posts: 34
Joined: Sat Jan 19, 2013 3:00 pm