Good Caps Low ESR

[killian6pk]

When buying Low ESR caps at what point (uf rating) do you have to quit worrying about ESR and just buy general purpose caps. For example: I was looking for 2.2uf 50v and had a hard time locating any.

Also it appears Digikey is phasing out Aluminum Electrolytic Caps and going with the small Solid Caps that look like SMD but with leads. Mouser also seems to be doing this. If there is a Solid Cap in the size needed to replace an Alum. Cap on a board can you use them?

[PCBONEZ]

Re: Good Caps Low ESR

I don't unless the original was a GP and I absolutely can't find one in low ESR.
In that case I look for the GP with the highest Ripple rating.

I'm really not seeing a problem with your example though.
I found 2.2uf 50v available in FC, PW, and KY in one try on Digikey.

Digikey and Mouser aren't phasing out anything.
Their suppliers are and that's in response to the way they think the market is going.
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[Longbow]

Re: Good Caps Low ESR

When buying Low ESR caps at what point (uf rating) do you have to quit worrying about ESR and just buy general purpose caps.

Good question. It is incorrect to assume that every capacitor in a given device needs to have some arbitrary ESR value. Putting it another way, replacing a GP cap with a computer grade cap will not hurt anything, but it also will not make the circuit work better. In order to make a judgement call, you have to know what you are working on, and what the circuit is supposed to do. There you have it.

[PCBONEZ]

Re: Good Caps Low ESR

That's not what replacing GP with low ESR is about.....
Low ESR caps nearly always have higher Ripple Current ratings...
They are also generally higher quality caps. [They have to be.]
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When buying caps a few at a time [less than several 100's] there is not a significant cost difference between buying 'entry level' low ESR or GP so it simply makes sense to buy the higher quality part that handles more ripple.
It will last longer if nothing else.
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And contrary to the 'won't make it work better' thought.
- There's a significant number of posts here that have shown otherwise.
Often a low ESR cap should have been used but were not - in aid of 'cheaping down' the production cost down.
[They buy caps in 10,000's+ quantities not 1's, 10's, 100's like most of us.]
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Antec PSUs are great examples of that.
Antec often used Fuhjyyu TN series in PSU final OP filters.
TN are not low ESR as should ALWAYS be used in PSU final OP filters.
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If you think lots of other companies don't do that [particularly with smaller caps 'no one will notice'] every chance they can then you're nuts.
They do. - Even on mobos sometimes.
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When working on PC/IT related stuff [and Monitors/TVs] I'd bet 1/2 the GP caps you come across should have been low ESR to start with.
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Then there's the little detail that sometimes you WILL run across a small cap that's low ESR as it should be.
Are you going to stock that size in -both- GP and low ESR for when that comes up?
- For me it's more cost effective to order one size that works in either situation than to order small quantities of two different caps.
[Also takes less storage space and makes inventory easier.]
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[killian6pk]

Re: Good Caps Low ESR

Thanks for the info. I was using the 2.2 as an example. I had found them on Mouser also. I did not get an answer (I don't think) about the solid caps and if you can use them in place of the normal Electrolytic's that we are using now.

[PCBONEZ]

Re: Good Caps Low ESR

""" if you can use them [sic: solid poly] in place of the normal Electrolytic's that we are using now. """
That totally depends on the circuit in question.

When it comes to small uF values what you will often find that polymer are too large to replace a small can lytic.
[Not always, just often. Things have been getting better that way.]
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You'll also find that polys in higher voltages are either non-existent or very expensive.
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For instance the 2.2uF 50v you asked about...
The highest voltage I can find [Mouser] in a 2.2uF poly is 30v.
[And it's listed as no longer available.]
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Then looking for 100uF 16v in poly [common size on mobos] at Digikey.
The lowest (per-each) price for poly is $0.64.
That size in panny FR is $0.33 per-each.
For 50pc the FR work out to ~$0.15/each and the Poly to ~$0.47/each.
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The common sizes of Poly [like used in VRM's] are a different story.
Sometimes they are cheaper than Lytics now.
I think that's due to the huge demand for those sizes for mobos and higher production.
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BUT: Things in "Cap Land" are changing pretty fast.
Old series are going *poof* and new ones are popping up often lately.
- Don't expect things to be the same a year or two from now.
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[killian6pk]

Re: Good Caps Low ESR

Thanks Grumpy Old... I was going to say fart, but I are one too. I have one more question not on this subject, but caps in general. Most of the Power Boards in Monitors that I am working on have large rectangular caps (polyester I think) usually they are near the AC input and the fuse. Do these have a habit of going bad over time like Alum. Electr. Caps do? Just thought of a second question. I don't see Elite Caps on the good or bad list. What is your opinion of them. I see them a lot in boards.

[PCBONEZ]

Re: Good Caps Low ESR

Those are usually Metalized Polyester Capacitors.
They sometimes are called the X Capacitor on drawings or PCBs.
It plus the Y Capacitor(s) and a coil make up the Input Filter which keeps EMI from the power line out of the PSU and EMI from the PSU out of the power line.
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Those rarely fail short of a bad power surge in the power line.
I've never seen a bad one in anything that was still in good enough shape I cared to fix it.
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[ipman]

Re: Good Caps Low ESR

Sometimes I found GP caps with lower ESR than Capxon Low-ESR ones, so I procedeed to replace the bulged Capxon with those.
So far, no problems. Any advice anyway?

[PCBONEZ]

Re: Good Caps Low ESR

Sometimes I found GP caps with lower ESR than Capxon Low-ESR ones, so I procedeed to replace the bulged Capxon with those.
So far, no problems. Any advice anyway?

That sounds okay if the GP caps are good brands, the ripple is good enough, and you live in one of those places where good caps are hard to get your hands on.
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