Electtrolytic Capacitor Becomes Hot

I always use 105C capacitors. It's well worth it.

There may be some other fault in the power supply resulting in the capacitor heating. And capacitors with a higher temperature rating may have a higher ESR, which would result in more heating if there is excessive ripple current or something like that.

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It's probably a high ripple current filter capacitor. Get a good high frequency, high ripple current 105 degree cap. Panasonic FC, Nichicon PW or HE series are 3 good choices.

Are you sure of this or is this a typo ?

I understand that 105 Centegrade types are higher quality / SMPS rated capacitors. If anything affects the ESR, I would expect those capacitors to have a lower ESR value, not higher.

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Kind regards,
Gerard Bok

I suspect the full wave bridge is not anymore - a diode in it is shorted and the poor capicitor is dealing with a half wave rectified, rather than full wave... put a scope on it and see !

Rick - Atlanta

You should be using a 105C rated cap.

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JANA _____

The router is continuosly on (has been so for the last week) and the replaced capacitor again feels slightly warm to hand (as warm as the external power adapter); although there are no problems with the operations of the router. The only other parts before the capacitor are a filter and 4 rectifier pair; the external power adapter supplies 9V AC.

The capacitor is rated to be used upto 40 C and so I don't think there should be a problem or should replace it wth a higher rated capacitor ?

Thanks

On Fri, 23 Dec 2005 13:10:39 GMT, "Indu Prakash" put finger to keyboard and composed:

I may be demonstrating my ignorance, but I don't recall ever seeing a

40 deg C electrolytic capacitor, only 85C and 105C.

- Franc Zabkar

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Please remove one 'i' from my address when replying by email.

I still have several 40 deg C capacitors in my old junk parts bin of parts used in stuff from the late 1960s and early 1970s.

I'd have to see a 40 deg C rated cap to believe it. 40 deg C=104 deg F. No way. Back in the 60s there really was no electrolytics other than the multisection filters and they were rated at 85 deg C, then in the

70s when electrolytics began appearing as small capacitors they really never even showed a degree rating on the majority of them, the ones that did was 85 deg C. Then in about 1985 the first 105 deg C caps began to show up. This is the way I remember it anyway. Of course all caps are different, a 85 degree may have a higher ripple current rating from one manufacturer than a 105 degree rated one from another. The high ripple current will cause the cap to run hot, as well as being placed next to high heat resistors ect. so on top of the temp rating, keep in mind the ripple current rating too. I always use the best qualty highest rated ripple current caps @105 degree C rating. No use using scum capacitors as the best still only cost about $0.20 to a couple dollars depending on the size. Don't use scum and save $0.05 or you'll be replacing them every 6 months.