3 lead electrolytic capacitors
Old 30th October 2011
  #1
Gear nut
 
noizek@t's Avatar
 

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3 lead electrolytic capacitors

so...

My friend is replacing visibly bad caps on his motherboard with ones that match other than their physical size and the fact that they have a third lead coming off of the top. I have head of 3 lead ceramic caps, but not electrolytic caps. These were the only ones that he could find that matched at our local stripped parts store in Colorado Springs. My question is the same as his, can he clip the third lead (probably ground) and have it function like a two lead, or does he need to ground the third lead, or is this cap not going to work at all for his needs?

thanks ahead of time

bsp
Old 30th October 2011
  #2
Lives for gear
 
idylldon's Avatar
 

Sounds to me like he bought two-section caps; that is, the one solo lead is the ground and the other two leads are the + side of each section. My guess is that they won't really work for his situation because the caps he's replacing are most likely single section with plus on one lead and negative on the other. You could possibly kludge what he bought to work, but caps are so cheap you might just as well do it right.

Do you have a pic?

Cheers,
--
Don
Old 30th October 2011
  #3
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noizek@t's Avatar
 

Thread Starter
Quote:
Originally Posted by idylldon View Post
Sounds to me like he bought two-section caps; that is, the one solo lead is the ground and the other two leads are the + side of each section. My guess is that they won't really work for his situation because the caps he's replacing are most likely single section with plus on one lead and negative on the other. You could possibly kludge what he bought to work, but caps are so cheap you might just as well do it right.

Do you have a pic?

Cheers,
--
Don
Sounds about right... I don't have a pic, but they are bright blue, 5 or 6cm long and 2cm in diameter. Very odd, old looking, and clinical. They are probably new old stock military caps since we have 4 military bases in Colorado Springs including NORAD.
Old 30th October 2011
  #4
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Minion's Avatar
 

They are either 2 section caps , or ,some caps have a third leg to add stability , especially for caps that are large and will be used in applications where there could be a lot of Vibrations that could over time weaken the legs or the solder joint......
Just test with your DMM if there is any connection between the 3rd leg and the other 2 legs .....

Cheers
Old 30th October 2011
  #5
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noizek@t's Avatar
 

Thread Starter
Quote:
Originally Posted by idylldon View Post

Cheers,
--
Don

Oh, and thank you very much for the information. We are both beginner level and need all of the help that we can get since there is no analog electrical engineering schooling available in the state.
Old 30th October 2011
  #6
3 + infractions, forum membership suspended.
 

Quote:
Originally Posted by noizek@t View Post
Sounds about right... I don't have a pic, but they are bright blue, 5 or 6cm long and 2cm in diameter. Very odd, old looking, and clinical. They are probably new old stock military caps since we have 4 military bases in Colorado Springs including NORAD.
i would not use old norad caps for anything

especially electrolytics

spring the bux for new ones
you will save that many times over in not wasting time and rework and troublshooting
Old 30th October 2011
  #7
Gear nut
 
noizek@t's Avatar
 

Thread Starter
Quote:
Originally Posted by Minion View Post
They are either 2 section caps , or ,some caps have a third leg to add stability , especially for caps that are large and will be used in applications where there could be a lot of Vibrations that could over time weaken the legs or the solder joint......
Just test with your DMM if there is any connection between the 3rd leg and the other 2 legs .....

Cheers
thanks, I will tell him to test them.
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