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Polarized cap or no?

Mark Makelky

Mark Makelky

New Member
I need to replace this capacitor and would like to know for sure if this 4.7uF 35v electrolytic is polarized. Guessing the brand is PVAN- both caps in foreground are the same. Can't readily identify a polarity marking, could the brand name be the negative terminal? One terminal is labeled with specs, the other is just the brand. All other PVAN electrolytics on this board are clearly marked for negative but these little ones are not. Circuit is on a subwoofer amplifier board.

Thanks in advance for any help
Mark
Polarized or not.jpg
 
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Are there any polarity markings on the circuit board? If not, I'd say they're NP.....
 
+1 on using Nichicon ES

It would appear to be a non-polar (bipolar) cap, but I can't read the markings clearly, so can not say for certain. But even if it is not non-polar, it does no harm to use a non-polar cap. Go up in voltage rating and use 4.7uF 50V
 
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Thanks for the responses. To aid the discussion I offer the following:
No schematic available..... Top secret... proprietary information.... blah.... blah
Upon closer inspection, I do kinda see the NP shown outside and on both ends of the brand name
No markings on board in this vicinity that might help
I wondered what would be the consequences of using a non polar cap even if its supposed to be polarized... thank you for that comment
I will shop for the Nichicon ES caps suggested

Here's another photo zoomed in on the two identical caps that hopefully help you see and read all the markings from both sides. Is CD71 significant?
4.7uF.jpg
 
CD71 is probably some date or lot code.
Looking at some other examples of the IIPVAN capacitor brand they do put a white stripe in as negative, and seems that it doesn't have one, it suspects to be bipolar. However pretty much every bipolar electrolytic capacitor I've run across have "B.P.", "N.P.", or have two + symbols on the jacket... so indeed this is strange...

Reverse engineer of the board would be interesting or perhaps seeing where the capacitor is connected might give clues.

Main problem with bipolar electrolytic capacitors is that their ESR is significantly worse than polarized capacitors, but for audio use it may not be as critical.
 
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Mark Makelky said:
Thanks for the responses. To aid the discussion I offer the following:

I wondered what would be the consequences of using a non polar cap even if its supposed to be polarized... thank you for that comment


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Using non-polarized capacitor in place of a polarized capacitor is fine (though this is not likely the case here - based on the application I would expect this is indeed a nonpolarized capacitor.
 
cademan said:
Just curious. How do you know it needs to be replaced? Have you tested it?
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Ahhhh,,, now THAT is a great question! Short answer is: I don't, but I want to replace it anyway. This thing has an intermittent cut out problem. Doesn't blow fuses, just cuts out- and magically - cuts back in again. By a "very scientific and precise process" I figured out there something funny at this capacitor. By touching the top of it in operation I can make the unit cut in and cut out. Since it looks like I might be able to remove it and replace without tons of difficulty, I thought I'd give that a shot first. I'll test it when its removed. If the cut out remains after replacement, I got a short or something else goofy in this vicinity. Visually all looks to be pretty good. Actually the unit is brand new, so I wouldn't have thought a component was bad already... but...

I have a muuuuch longer and more complicated answer to this question, but there are probably forum rules about how long a post can be and once I get started ranting its hard to shut me down......
 
As Gadget73 said, replace it with a film cap. It's only a 4.7uF so you can get that value in a 50V for peanuts.
 
...agreeing with the last few posts about re-soldering. But I would also look at all the other solder joints in the area of those caps. If pushing on one of them causes cut-out, it could be that a slight flex in the PCB is causing loss of contact in some difficult to see, nearby joint. Sub woofer amps have a very hard life...constant vibration and heat can not escape as it would in typical amps.
 
roger2 said:
...agreeing with the last few posts about re-soldering. But I would also look at all the other solder joints in the area of those caps. If pushing on one of them causes cut-out, it could be that a slight flex in the PCB is causing loss of contact in some difficult to see, nearby joint. Sub woofer amps have a very hard life...constant vibration and heat can not escape as it would in typical amps.
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Absolutely, and even joints that look fine are never above suspicion. Sometimes they separate from the solder pad and will look fine from above.

Recommend using some paste flux to reflow or you may get a cold joint. The flux will clean the solder pad as it boils off as well.
 
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