what to do if a cap is not listed on its datasheet

[markcoenen]

I have a Dell 2005fpw monitor that i'm replacing the caps on the main board.
It has at least 1 Samwha cap 22uF 25v RD series that does not have an entry in the ripple current table. Datasheet attached. Looks like it's a 5x12mm.

Why might a cap be missing from the table?
What do I do for a ripple current value?

thanks

[Behemot]

Re: what to do if a cap is not listed on its datasheet

Custom size. It's GP cap, so use GP again. If you know exactly where it is and what it does and it is possible to use low-ESR or at least long-life cap there, you can use that.

[markcoenen]

Re: what to do if a cap is not listed on its datasheet

"Custom size"! That I would not have guessed.

Looking at the datasheet, do you think it is reasonable to to guess at a approximation for my mystery custom cap? I would guess 66mA of ripple. I ask because I want to know if my reasoning is valid.

By "GP" I assume that's "General Purpose"?
I know where it is but not what it does. I don't have the knowledge yet to make a guess. The main board in a monitor (this monitor) looks like a video card. I imagine it is a computers video cards' counter part, one encodes a video signal the other decodes. Other then that it's beyond me and, i'm not sure of that guess.

Now I am noticing that there are many caps that don't have ESR or impedance values listed in it's datasheet. In those cases, when selecting replacement caps, would any value work? Is there a general rule to guide me in these cases? Maybe a "middle of the road" value?

I am surprised at how complex a simple looking part can be. The more I learn the more I think art and science are the same thing.

[Behemot]

Re: what to do if a cap is not listed on its datasheet

In the beginning there is usually statement about what type of cap it is. If it states general purpose, you don't need to exactly match it, any decent general purpose series will do. E.g. NCC KMG, Rubycon PX.

Some types, usually general purpose, long-life or high-voltage caps do not list impedance.

[jazzie366]

Re: what to do if a cap is not listed on its datasheet

I have a Dell 2005fpw monitor that i'm replacing the caps on the main board.
It has at least 1 Samwha cap 22uF 25v RD series that does not have an entry in the ripple current table. Datasheet attached. Looks like it's a 5x12mm.

Why might a cap be missing from the table?
What do I do for a ripple current value?

thanks

That's a teeny cap. I would get a cap of similar type and size, but higher ripple current handling and same ESR.

The thing is, ESR is listed but generalized across voltage and temperature, so that means these caps are literally basic general caps with wide temperature handling, which is necessary for this application. Monitors get warm, hot, cool, and all over the place in their environments. So get something similar. You'll never see the -55 so IDK why they used a cap with that low of a temperature rating, just get one of these and you'll be good to go:

http://www.ebay.com/itm/25-PCs-AL-CA...cAAOSwjVVVyo8Q

Here's the datasheet:
https://cdn.badcaps-static.com/pdfs/...a9532291c7.pdf

Twice the estimated ripple of those SamWha's, I'd personally go with these.