Testing polarity of Eltrolytic Cap - diyAudio
Go Back   Home > Forums > General Interest > Everything Else

Everything Else Anything related to audio / video / electronics etc) BUT remember- we have many new forums where your thread may now fit! .... Parts, Equipment & Tools, Construction Tips, Software Tools......

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 18th September 2006, 10:59 PM   #1
jkeny is offline jkeny  Ireland
Banned
 
Join Date: Feb 2007
Location: Dublin
Default Testing polarity of Eltrolytic Cap

I've searched but found nothing here. Can anybody tell me how to test which is the neg pole of an electrolytic cap. I have good electro caps with no jackets.

Thanks
John
  Reply With Quote
Old 18th September 2006, 11:39 PM   #2
diyAudio Member
 
Geek's Avatar
 
Join Date: Sep 2004
Are they axial? The end with the crimp is usually positive.
  Reply With Quote
Old 19th September 2006, 12:34 AM   #3
Enzo is offline Enzo  United States
diyAudio Member
 
Join Date: Sep 2004
Location: Lansing, Michigan
And if they are radial with wire leads, the positive wire is often longer. Snap-ins often color code the negative leg black.
  Reply With Quote
Old 19th September 2006, 01:55 AM   #4
poobah is offline poobah  United States
diyAudio Member
 
poobah's Avatar
 
Join Date: Nov 2005
In general, un-labeled might be bad news.

How do you know what the voltage and capacitance ratings are then?

How did they lose their label?

A little history? They may not HAVE a polarity (don't count it).

Backwards caps EXPLODE... really.

Send me a PM.



  Reply With Quote
Old 19th September 2006, 05:55 AM   #5
diyAudio Member
 
I_Forgot's Avatar
 
Join Date: Jan 2005
Location: Phoenix, Az.
But they sound so much better without their jackets!

I_F
  Reply With Quote
Old 19th September 2006, 06:20 AM   #6
clem_o is offline clem_o  Philippines
diyAudio Member
 
Join Date: Jun 2005
Location: Manila
I think this will work:


Set up a DC source, variable output if possibe. Put a resistor in series with the cap, i.e. 1K ohm.

SLOWLY increase the output voltage of the source, while watching the voltage across the resistor. Vr should always be zero. If it begins to rise, you probably have the polarity of the capacitor inverted - remove capacitor, short it, and re-insert the 'correct' way. Retry and confirm that the voltage across the resistor always remains zero.

Any idea what the voltage rating of the capacitor is?

Cheers!
  Reply With Quote
Old 19th September 2006, 07:26 AM   #7
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
that last process is similar to a leakage test.

Increase the resistor to 100k and then check the leakage vs the charge voltage.

When the leakage starts to increase suddenly with increased voltage you have probably past the maximum working voltage.
This same leakage increase (but at a much lower voltage) also indicates that you have it the wrong way round.

This will also reform the cap if it has been out of service or used on low voltage duty for a long time.
__________________
regards Andrew T.
  Reply With Quote
Old 19th September 2006, 09:19 AM   #8
jkeny is offline jkeny  Ireland
Banned
 
Join Date: Feb 2007
Location: Dublin
Hi all,
Thanks for the replies. I will be using this leakage test to test the viability of these caps

A bit of background - the nude caps are radial Panasonic FC 1,000uF 63V rated which were used before & I inherited them - so legs are already cut. A suggested way is to test continuity between case and lead (the neg lead should give continuity)

4 Pole caps are ROE 10,000uF 40V (X2) & 20,000uF 16V - these have their jackets & there is a vertical line running up the jacket in line with a pin that is marked on top with a (-) - I presume that this is the neg pole. The other pins are marked 1, 2, 3. I believe only one of these is the pos pole the other two are for fixing. How to test for pos pole then?

JOhn
  Reply With Quote
Old 19th September 2006, 03:33 PM   #9
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
Hi,
most electrolytics have the case isolated from the capacitor.
You might get a bit of leakage to the case but this should be very small. It may show up as a negative voltage on the case.
__________________
regards Andrew T.
  Reply With Quote
Old 19th September 2006, 03:46 PM   #10
poobah is offline poobah  United States
diyAudio Member
 
poobah's Avatar
 
Join Date: Nov 2005
If the pins are numbered... just look at the data sheet!

  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
Ess AMT polarity? Help promitheus Planars & Exotics 1 13th July 2007 09:52 PM
Hi-Vi B3N polarity Gollum Multi-Way 5 5th July 2007 05:58 PM
Polarity on OB sub icebear Subwoofers 3 29th April 2005 08:24 AM
LED polarity guitargully Solid State 4 12th January 2004 04:14 AM
Polarity Myren Multi-Way 6 22nd December 2001 01:44 PM


New To Site? Need Help?

All times are GMT. The time now is 12:32 AM.


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