Electrolytic Capacitor Blown up - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 6th March 2010, 06:50 AM   #1
diyAudio Member
 
Join Date: Dec 2006
Default Electrolytic Capacitor Blown up

Hi all,

I recently re-assembled a gainclone amplifier basically as per the datasheet. I noticed I had some very weak bass transients which didn't quite make sense to me. Anyway, after listening for about 15 minutes an electrolytic cap went kaboom. It was one of the supply caps on the circuit (Cs), not the main supply filtering cap. The cap is meant to be rated at 50V and the supply is about 37V +/-.

I've only ever heard about capacitors blowing when being used above their rated voltage. Is it common for cheaper (this was a cheap cap) to have this issue?

I'm a bit reluctant to replace and try again until I get some other thoughts.

Cheers!
  Reply With Quote
Old 6th March 2010, 07:23 AM   #2
Joris is offline Joris  Netherlands
diyAudio Member
 
Joris's Avatar
 
Join Date: Aug 2009
Location: Noord-Holland
Maybe I'm totally wrong, but did you observer the polarity before mounting it on the pcb? Caps don't like wrong way currents... Caps, even cheap ones, can handle voltages of 10% up to their rating. Don't know what quality your caps are though...
  Reply With Quote
Old 6th March 2010, 07:59 AM   #3
diyAudio Member
 
Join Date: Dec 2006
The polarity was definitely correct as per the marking on the caps - The cap may have been printed on incorrectly? The quality is just your run of the mill 2200uF cap 50V from a local electronics shop.

I've used plenty of them in other applications with no problems so is it possible this was just a dodgy cap?
  Reply With Quote
Old 6th March 2010, 08:10 AM   #4
Mooly is online now Mooly  United Kingdom
diyAudio Moderator
 
Mooly's Avatar
 
Join Date: Sep 2007
If the DC voltage across the cap is within the rating, and the ripple current passing through the cap is also within limits (a duff or wrongly wired bridge would do that) then it has to work OK.
New faulty parts... it shouldn't happen if they are of reputable manufacture. Loads of fake stuff around.
__________________
-------------------------------------------------------
Installing and using LTspice. From beginner to advanced.
  Reply With Quote
Old 6th March 2010, 08:12 AM   #5
diyAudio Member
 
Join Date: May 2008
Ive only had electrolytic caps explode when connected back to front or fed too many wheaties
__________________
Entia non sunt multiplicanda praeter neccissitatem
  Reply With Quote
Old 7th March 2010, 02:56 AM   #6
diyAudio Member
 
Join Date: Aug 2008
I've seen pictures of fake capacitors that were just a case over a lower voltage rating capacitor. If you got it at a local store, I would hope it wasn't a fake no-name capacitor
__________________
Tyler
  Reply With Quote
Old 7th March 2010, 10:48 AM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
an old electrolytic can have degraded to such an extent that it must be reformed before applying rated voltage to it.

If reforming is required and not done then the leakage current can be dangerously high and since these components are not designed to be self healing then explosion due to excessive heating could, in very rare occasions, occur.
__________________
regards Andrew T.
  Reply With Quote
Old 7th March 2010, 06:53 PM   #8
gfiandy is offline gfiandy  United Kingdom
diyAudio Member
 
gfiandy's Avatar
 
Join Date: Jul 2003
Location: Cambridge UK
It can happen with old electrolitics but normally you are talking valve amplifer old for this to be the case . I would guess it was incorrectly labeled, probably the wrong way round as caps can survive quite a high over voltage for a reasonable length of time especially if as you describe they are not the main smoothing cap so the ripple current is fairly low.

Regards,
Andrew
  Reply With Quote
Old 7th March 2010, 09:06 PM   #9
diyAudio Member
 
Join Date: Dec 2006
I'll just put my tail between my legs now.... Turns out I had connected it (in the correct polarity at least) from the positive to negative rail instead of positive to ground. Just a complete mental blank on my behalf when I put it all together.

Anyway, the poor 50V cap which I was so quick to judge had about 75V across it. Sorry cap!
  Reply With Quote
Old 9th March 2010, 07:29 PM   #10
tomchr is offline tomchr  United States
diyAudio Member
 
tomchr's Avatar
 
Join Date: Feb 2009
Location: Greater Seattle Area
Well... Let's just say you took it out to the farm so it could run free...
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Electrolytic Output Capacitor Kashmire Pass Labs 30 13th December 2007 10:59 AM
electrolytic capacitor source oldheathkitphil Parts 2 22nd June 2007 08:25 PM
Very Newbie Question - Is this a electrolytic capacitor? zBuff Parts 1 11th July 2006 03:05 AM
electrolytic can capacitor el capitan83 Tubes / Valves 3 18th December 2004 05:01 PM
Electrolytic Capacitor Insulation runeight Tubes / Valves 2 22nd December 2003 07:20 AM


New To Site? Need Help?

All times are GMT. The time now is 06:00 PM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2