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I'm looking at two capacitor data sheets for some blow caps in my KBNBX-LA motherboard. Here is a pictures of the caps on the mobo.

bad caps

Caps read 6.3v 3300uF

The caps read Rubycon 6.3v3300uF MBZ. I was able to find these exact caps on eBay, and and Amazon. But, they were pretty expensive. I couldn't find them on Digikey (which was sort of a red flag to me). I went to Rubycon direct and I was able to find the datasheet on the MBZ series. The MBZ series is titled, "105 deg C Ultra Low ESR for PC mother board." However, they no longer sell the MBZ series. There is no mention of what they replaced it with, but it seems like it was replaced with the ZLJ series which is titled, "105℃ Long Life, Low Impedance, High Ripple Current."

It's also kind of interesting the the MBZ series has a higher ripple current at 6.3v 3300uF at 3230, than the LZJ at 2250.

My question is using the two spec sheets above, is the ZLJ series the replacement to the MBZ series? What's the difference? Long Life sounds like an upgrade? Is there any downside?

I don't understand much of what ripple current even is. I'm pretty new to this.

Search the Rubycon site?

Got a second and think I picked the wrong alternative, here is the Rubycon product search. Maybe I didn't even do that right.

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closed as off-topic by Andy aka, EM Fields, PeterJ, Daniel Grillo, Nick Alexeev Nov 9 '15 at 8:11

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "Questions on the repair of consumer electronics, appliances, or other devices must involve specific troubleshooting steps and demonstrate a good understanding of the underlying design of the device being repaired. See also: Is asking on how to fix a faulty circuit on topic?" – Andy aka, EM Fields, PeterJ, Daniel Grillo, Nick Alexeev
If this question can be reworded to fit the rules in the help center, please edit the question.

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    \$\begingroup\$ When the capacitor rot issue came to light many lines of electrolytic were discontinued. What you are seeing on ebay is someone trying to drop the last amount of NOS material they have on hand, at the unlikely chance that someone would need it desperately (sometime contractual repair obligations), but in general this is a faulty component and should be replaced with ratings equivalent modern component. \$\endgroup\$ – crasic Nov 7 '15 at 23:51
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    \$\begingroup\$ NOS means New Old Stock, so basically unused components which were lying on the shelf for some years. It's not a material used in capacitors. \$\endgroup\$ – Arsenal Nov 7 '15 at 23:56
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    \$\begingroup\$ I'd go for Nichion UHM0J332MPD9 as it seems to be very close to the original datasheet. But even those are marked as not recommended for new designs and are probably an end of life product. Everything moves to SMD mounted capacitors, so the market for low ESR THT capacitors seems to be dying. \$\endgroup\$ – Arsenal Nov 8 '15 at 0:15
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    \$\begingroup\$ It's not silly - how can you possibly know what part to choose without a circuit and knowledge of what the darn thing is meant to do. Experts don't guess and only a fool would say that. \$\endgroup\$ – Andy aka Nov 8 '15 at 0:22
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    \$\begingroup\$ I tried myself with a generific answer to your generific (generic - specific) question, as I could see both elements present, one of which I deemed on-topic and the other I deemed off-topic (but used it as an example) - still not sure if it was the right choice to give advice on stuff which might go wrong quite often. \$\endgroup\$ – Arsenal Nov 8 '15 at 1:44
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When I repair stuff with broken capacitors I try to to go along this list:

  1. Identify broken capacitor
  2. Get a datasheet on that capacitor
  3. See if the exact part is still available as new part (I try to avoid old electrolytic caps found on ebay(NOS = new old stock), as they don't get better with age )
  4. Buy it and replace it

Most of the time though, it won't be available anymore. So I'm off trying to find a suitable replacement part.

For that I have to guess the function of the capacitor, as this determines the importance of certain specifications of the capacitor. Luckily most of the time the capacitor ends up being a power supply filter capacitor (some power transistors and coils are nearby as kind of an indicator). But sometimes it's something else (if I'm faced with that, I usually give up).

Common for all capacitors is the capacitance and voltage ratings. Voltage rating must be at least the same value, but can be higher without any drawback. Capacitance depends on the function, for power supplies a value higher than the original tends to be okay, lower is not, but both may cause trouble, so I stay on the original value if possible.

For power supply capacitors one of the most important values is the ESR (equivalent series resistance) or the ripple current rating (they sort of go hand in hand). Usually lower is better, but too low can cause stability issues, too high can lead to those as well. As I don't know the specifics of the voltage regulator requirements, I try to stay very close to the original specification.

A trap here is that the value can be measured at different frequencies and is thus not always comparable right out of the sheet - sometimes you will find a table to calculate the ESR at different frequencies in the datasheet.

The next thing I try to achieve is physical specs meeting the original part. So I look for diameter, height and pitch of the leads. You can get away with different sizes and stuff, but it looks dead ugly and you can get shorts if you have to bend the leads all over the place to make them fit in the case. Pitch would be most important to be the same, diameter can be smaller, height can be smaller.

Last thing I try to get right is the operating temperature and rated lifetime. Operating temperature is simple, the higher the better and same goes for rated lifetime. I wouldn't go lower on the operating temperature rating (caps just die really quickly when they get too hot), but for rated lifetime I would.

Armed with that knowledge, parse the original datasheet, head over to a distributor with a nice parametric search engine and filter the results according to the found data. If you find that a parameter seems to be filled erratically, omit it and filter the datasheets by hand on that parameter. ESR is likely one of them.

(note: parsing datasheets requires great care as they often contain data on whole families and one can easily pick the wrong numbers)


For your parts (as seen on the picture they seem to be power supply caps as well).

The MBZ datasheet tells us:

  • 6.3 V
  • 3300 µF
  • 12 m\$\Omega\$ ESR @ 100kHz
  • 2800 mA rms ripple current @ 100kHz
  • 10 mm diameter, 23 mm height, 5 mm pitch
  • 105°C max
  • endurance rated at 2000hrs

The ZLJ datasheet:

  • 6.3 V
  • 3300 µF
  • 24 m\$\Omega\$ ESR @ 100kHz
  • 2250 mA rms ripple current @ 100kHz
  • 10 mm diameter, 25 mm height, 5 mm pitch
  • 105°C max
  • endurance rated at 10000hrs

I have put the values in bold which would make me look for better alternatives. It has double the ESR and a reduced ripple current capability. And it is a bit higher (on a motherboard that probably won't matter).

So I went over to Digikey, and searched for electrolytic capacitors with the specs given. As it turns out, the ESR filter is quite useless, so I didn't use it. For the voltage filter I selected a minimum of 6.3 V, for the height a maximum of 23 mm. Basically, do not filter too strictly, there are advancements in technology (yay) which might allow for higher voltage ratings in same housings, so we don't want to exclude those when filtering.

I ended up with a pretty small list of 15 or so capacitors, from which only 6 were actually different (due to different packaging, some get listed multiple times). From all of those the Nichicon UHM0J332MPD9 seemed to be the best fit:

  • 6.3 V
  • 3300 µF
  • 13 m\$\Omega\$ ESR @ 100kHz
  • 2800 mA rms ripple current @ 100kHz
  • 10 mm diameter, 20 mm height
  • 5 mm pitch
  • 105°C max
  • endurance rated at 2000hrs

It's actually available in 12.5 mm diameter with 20 mm height and 10 mm diameter and 25 mm height as well, you have to be careful which part number you exactly get. The twelfth digit will tell you which size it is: 6 would be the 12.5 one, 9 is the 10x20 mm and 3 is the 10x25 mm. (see the very bottom of the datasheet, even that is important)

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    \$\begingroup\$ This is tremendously useful for someone like me, all around. And, it's exactly what I'm looking for. I would hope that if this question is closed in the future, at any time, you're moved to write a blog on this kind of stuff. Thanks. \$\endgroup\$ – Evan Carroll Nov 8 '15 at 8:24
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    \$\begingroup\$ @EvanCarroll: the question was closed because of the mixture of specific and general advice asked. I'm on the fence on this issue [closure]... Anyway, reopening the question won't result in much better general advice than already provided. And the specifics of your circuit are lacking. In general, the output cap ESR for some type of switching supplies [and also for some linear regulators, especially LDOs] needs to be in a certain band; neither too high nor too low. Going outside this band can cause instability/oscillations. (to be continued) \$\endgroup\$ – Fizz Nov 27 '15 at 9:14
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    \$\begingroup\$ Here's an article with some examples of the subtleties involved: edn.com/design/components-and-packaging/4371879/… (The link was too long to paste it in the previous comment.) \$\endgroup\$ – Fizz Nov 27 '15 at 9:15

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