Is there anything else to look for in replacement caps other than F and V ratings?

**mariushm** · 12-04-2015, 06:59 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

Capacitors designed for switching power supplies are Low ESR. You don't see "low esr" because this is a relative term.

In most circuits you would see (computer power supplies, monitor power supplies, etc) the capacitors are in circuits that operate at high frequencies (typically over 60kHz) - at such high frequencies the ESR tends to be almost equal to the impedance of the capacitor.
Therefore, it's easy to approximate the ESR of a particular capacitor by looking in the datasheet for the series of that capacitor at the column titled Impedance at 100kHz and some reasonable positive temperature.

Your new capacitor should normally have an ESR/Impedance value very close or just a bit lower than the value of the old capacitor. In some circuits you can use capacitors that have much lower ESR without problems, but other circuits are more "picky", so it's best to stick with "very close or a bit lower (by a few percentages)"

The ripple current is also important, the capacitor you use to replace an old one should have a ripple value very close to the old one, ideally equal or better than the old one.
This ripple current is also specified in the datasheet for a particular series of capacitors.

The capacitance should remain the same. In some cases, you can go with the capacitance a step higher without any problems.
In some special cases (don't do it if you don't understand the circuit), regular electrolytic capacitors can be replaced with polymer capacitors of much lower capacitance.

You can install capacitors rated for a voltage higher than the rating of the old capacitor. In fact, this makes it possible sometimes to install a capacitor closer to the old capacitor's ripple and esr values... the downside is that higher voltage rated capacitors are usually larger in diameter.

I have a large collection of capacitor datasheets here : ftp://helpedia.com/pub/temp/datasheets/capacitors/
Feel free to read the datasheets for your old capacitors and determine the ripple current and esr, to make it easier for you to choose new capacitors.

**Yamashiro** · 12-04-2015, 07:23 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

Oh wow I actually found those old caps there:

I think I understood what you said, it looks like the site I'm buying it on doesn't list ripple current or impedance, is there an easy way to look for matching values other than check one by one?

**Yamashiro** · 12-04-2015, 07:37 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

Ok NVM, I searched Rubycon's site and found an exact match, that was helpful, thank you.

**Behemot** · 12-04-2015, 08:06 PM

Re: Is there anything else to look for in replacement caps other than F and V ratings

What were you looking for?

**Yamashiro** · 12-05-2015, 04:39 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

1000 uF, 16V RC: 1820 IMP: 0.023, DxL: 10x20mm.

So NICHICON - UHD1C102MPD and RUBYCON - 16ZL1000MEFC10X20 are perfect matches, I can buy the latter for about 13USD for 5 pieces from a local supplier including shipping.

**Behemot** · 12-05-2015, 04:52 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

If it is for that display power boar you got in next thread, for that purpose you can use everything as long as it is at least somewhat low-ESR, trust me, I have already repaired couple dozens of them…real ESR of those caps was much higher for years and it was still working. If you think it is still high, you can fill those vacant spots with more caps in parallel where the overall ESR will drop.

I can supply you with NCC KYB 1000/25, 0.037 ohm/1650 mA, 10000 hours, they will work more than fine. I got 10 pcs for aprox. 7 USD incl. shipping. Check stock, you may take more of them, incl. custom caps for ATX PSUs.

**mariushm** · 12-05-2015, 04:54 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

You can buy from Farnell, they have an Israel targeted version of their site.

Panasonic FM 1000uF 16v (better ESR and ripple current) 5000h@105c: http://il.farnell.com/panasonic-elec...rad/dp/1219463

Panasonic FR 1000uF 25v is even better, with bigger lifetime rating 10k @ 105c : http://il.farnell.com/panasonic-elec...rad/dp/1907238

Rubycon ZLJ 1000uF 25v would also work, even with a slightly higher esr (28mOhm vs 23mOhm , it's close enough to work just fine as replacement), also 10k @ 105c : http://il.farnell.com/rubycon/25zlj1...rad/dp/1831277

The Panasonics are cheaper than Rubycon, especially in quantity, and they're just as good. The Rubycon ZLJ is probably cheaper compared to your choice.

Shipping shouldn't be more than around 5$ and they should get to you in 2-3 working days. I use Farnell often and they're great.

**Behemot** · 12-05-2015, 05:00 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

mariushm: my caps cost less than half of Farnell

**Yamashiro** · 12-05-2015, 05:02 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

Thanks guys, I'll check it out.

Also, is higher RC better?

**Behemot** · 12-05-2015, 05:03 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

Yep, generally it is.

**mariushm** · 12-05-2015, 05:07 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

I buy in batches of 50-100 pcs when I need to (rarer these days). So a single 1000uF 25v Panasonic FR capacitor would cost me about 0.3-0.4$

If I had a lot of them in "stock" I would have offered to mail some to him for the purchase price plus about 2$ for postage, so less than your offer. But again, I have too few in my box of parts (I think i'm down to about 8-10 pcs of that capacitance/voltage rating) and I'm not in the mood to deplete my stock and then be forced to order a fresh batch.

And the ones I suggest match or exceed the specs, yours doesn't. In reality, if it's a monitor power supply as you say yours will probably work perfectly fine, but if he has choices why not buy the right parts from the start...

**Behemot** · 12-05-2015, 05:35 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

Those caps are overrated for that purpose, usually much worse are used for this application. Yet they failed anyway. I opted for KYB because of lifetime, if I took anything else, in about 90 % of other cases you would be screaming that they have too low ESR and it will be bad too etc. etc. I have been using KYA so far which have even higher ESR and everything is working OK for years now.

If you buy 100 pcs, you would still get them for about 24c a piece from me. So maybe next time consider dropping me a message. And I can also ship slow uninsured letter, but I won't because it is, eh, slow and inunsured maybe?

According to your post calculator, recommended letter 50-100 g costs 17.8 plus VAT over 22 Lei, which equals to over 5 bucks. And since it does not support declared value to Israel, I am not completelly sure whether it is even insured.

**mariushm** · 12-05-2015, 06:04 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

Put the capacitors in a matchbox, use more than 1 matchbox if needed, put the cardboard boxes in a A5 bubblewrap envelope and mail using regular mail.

The matchboxes plus bubblewrap give enough protection for pressure from other envelopes, weight, shocks, twisting, and the size of the matchboxes is below the maximum height allowed for non-commercial mail (they treat the envelope as someone sending a notebook to a friend)

2 lei for envelope (half for 100+ envelopes), about 10 lei in postage for anything up to 100 grams, vat included. 1$ = ~4 lei.
This standard shipping estimates up to 90% of mail to arrive to destination in 5 working days, expedited was doing it in 3 working days (guaranteed for about 80% of mail).

When I used to sell my excess stock on eBay, I shipped like this all over Europe (Ukraine, Russia, Poland, Portugal, UK, Spain, Montenegro etc) I had no complaints.

ps. I agree it's not "professional", not what a person would expect to receive from a company, but it worked very well for me.

**Yamashiro** · 12-05-2015, 06:15 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

Isn't Romania in the EU? How come you don't use Euro?

**mariushm** · 12-05-2015, 06:21 AM

Re: Is there anything else to look for in replacement caps other than F and V ratings

This site has a lot of US viewers, so I try to make it easier for them when talking prices. I try to look on the left side at who I'm replying to and where he/she is from but it's just easier to assume he's in US or knows his local currency to USD exchange rate.

It's also easier to just type " x RON to USD" in Google to get the value in dollars, euro is one letter more and I'm lazy

.

Romania is in EU but the local currency is still RON (romanian "lion", or "lei" which means "lions" in English). We don't work with euro yet (probably in 3-5 years if the exchange rates remain good)

So I'm ordering from Amazon UK in uk pounds, from ro.farnell.com in RON, paying euro on tme.eu ... it's a mess, it's easier to just convert everything to dollars when discussing things on a US based forum.