Difference between 3 pin and 2 pin capacitor - diyAudio
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Old 26th September 2001, 08:52 AM   #1
swede is offline swede  Switzerland
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On http://www.brigarelectronics.com/Mer...tegory_Code=CG I found a three pin capacitor.

What is actually the difference? Can I use it in a powersupply?

Sorry if I'm stupid, but I've never seen a three pin cap. before.

Have a good one,
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Old 26th September 2001, 03:19 PM   #2
tvi is offline tvi  Australia
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You will most likley find the third pin is left unconnected, they are their to stop such a big cap from pulling out one of the other pins during times of mechanical stress, shipping etc.

Hopefully the cap is marked, I had some ROE caps with 4 legs, 2 were dummy pins but the Cap had no marking as to what were what, most annoying

<font size="+0" color="#008080" face="timmons">Regards
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Old 26th September 2001, 04:12 PM   #3
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Another possibility, although I can't tell from the picture, is that the can actually contains two capacitors. I have a number of caps on hand that have a common ground and two or more pins for seperate caps in the same casing. It's not as common as it used to be, but there are still some to be found.

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Old 25th October 2002, 01:32 PM   #4
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I've juste got two caps out of an older amp, and they to have 3 pins! It seems that ground is common, and it charges on both the other pins, but there isn't really a way of checking that it charges correctly, is there??

Isn't marked in any special way, just says 44V 6800 microF

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Old 25th October 2002, 02:15 PM   #5
Cobra2 is offline Cobra2  Norway
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Default 3.rd pin


I have some of them in my bin as well.

The 3.rd pin is often reffered to as a locating-pin, and is
just that, a dummy.- (and might help secure the cap).

Arne K
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Old 25th October 2002, 04:11 PM   #6
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My Zen V4 features a trio of 5 pinned Caps for each channel
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Old 25th October 2002, 04:55 PM   #7
G is offline G  United States
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Alright Taz! Where are the pictures of the Zen V4 on your website? Just to add to this thread I have found some 3 pin "computer grade" caps. The third pin is definately just for mechanical integrity. It should have no electrical connection. If it were a two section cap it would be MUCH larger.

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Old 25th October 2002, 05:42 PM   #8
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Default three pins

I think it is usually to keep the cap from being installed in a PCB with the wrong polarity. This happens with two pin caps on occasion with spetacular results on power up.

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Old 25th October 2002, 05:59 PM   #9
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Although the capacitor in the link undoubtly has an extra dummy pin, three pin caps exist for supression circuits. The usual "delta" configuration consists of two class-Y caps between the hot terminals and earth with a third class-X cap connected between the two hot terminals.

Here's a datasheet with a connection diagram:

Nice one,
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Old 25th October 2002, 06:36 PM   #10
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Default Third pin

I got a few of those caps from Brigar. The third pin is only for mounting. It makes the cap stable (eliminates wiggling) as well as acting as polarizing pin as Fred said.

For my case, I mounted them upside-down with hot melt glue, and ground off the third pin to avoid shorting anything with my connections.
Vince Harris
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