KZJ Series? (Dell Server Motherboard)

[bw1]

I've got a Dell PowerEdge motherboard here with two leaking 6.3v/1800uf KZJ's. I can't find a lot of information on these, but understand they're out of production and crappy anyways.

What would a recommended replacement be?

Thanks!

[ratdude747]

Re: KZJ Series? (Dell Server Motherboard)

they like to dry up as well... treat them like any bad brand.

[PCBONEZ]

Re: KZJ Series? (Dell Server Motherboard)

KZG and KZJ go bad without even bloating.
Just replace them.

KZJ are higher end than KZG.
Comparable to Rubycon MCZ, Nichicon HN, Samxon GC
.

[bw1]

Re: KZJ Series? (Dell Server Motherboard)

Thank you for the spec sheet!

From what I can see, the HN's and GC's wouldn't work, as their ripple is lower than the KZJ's. HZ looks closer, doesn't it? Any others you can think of?

[PCBONEZ]

Re: KZJ Series? (Dell Server Motherboard)

Dunno.
You didn't give the diameter of the caps, the model of the board, or where the caps are on the board.

Are the KZJ 6.3/1800 the 8mm or the 10mm versions?
[You can use 10v caps too.]
.
If they are all Vcore caps you could consider a polymer upgrade.
.

[yyonline]

Re: KZJ Series? (Dell Server Motherboard)

Thank you for the spec sheet!

From what I can see, the HN's and GC's wouldn't work, as their ripple is lower than the KZJ's. HZ looks closer, doesn't it? Any others you can think of?

HN, GC, and KZJ are a near-exact spec match for the same can sizes. Yes, the ripple specs for HN are about 1% lower than KZJ. However, manufacturers routinely use these two series interchangeably, so they are close enough to not matter. No manufacturer is going to design a board to use capacitors within 1% of their max rating.

HZ has better specs than KZJ/HN. It would be okay to replace KZJ with HZ on most motherboards, but you have to be careful about changing the specs too much elsewhere.

[bw1]

Re: KZJ Series? (Dell Server Motherboard)

Sorry - forgot to mention the size. 10x16mm.

I don't have the board here, as it's still in service; I was addressing low hard drive space and I always do a full visual for things like this.

I don't have a picture of the EXACT board, either, but the board in the picture is close enough to give you an idea of which caps these are.

There are a total of three, with two showing signs of failure.

[PCBONEZ]

Re: KZJ Series? (Dell Server Motherboard)

Okay then.
The 10mm 6.3v KZJ can be replaced with 10mm 10v in HN, GC, or MCZ.
The larger [longer] can will get the ESR and Ripple in range. [Actually it's an upgrade.]
Gives you more options of caps to order and will probably cost less than HZ.
.
You should replace all the KZJ.
It's a problematic series and as some have gone south already the others are probably due to migrate and keep them company.
.

[bw1]

Re: KZJ Series? (Dell Server Motherboard)

10v HN it is. I believe you that the 6.3 would work -- they're not that far off at all. I just figured that 10v isn't really any more expensive, is a bit closer to correct, and is probably a bit more universal with the extras I'll have.

[PCBONEZ]

Re: KZJ Series? (Dell Server Motherboard)

Swapping 6.3v and 10v back and forth is an age old trick.
Mobo manufacturers used to do it a LOT.

Here's why it works:
-------------------
#1 - The caps rated voltage just has to be higher than the actual circuit voltage.

Mobos are fed 12v, 5v and 3.3v from the PSU.
[There are other voltages 'made' on the board but they are all less than 5v.]

You know a 6.3v or 10v cap is -not- on 12v.
- That means it's on 5v or less.

Both 6.3v and 10v work fine on 5v and less.
So: ON MOTHERBOARDS -> 6.3v and 10v caps are interchangeable.
[On something else you'd have to check the actual circuit voltage to go to a lower voltage.]

In a given series the higher voltage caps -usually- have a bigger cans than lower voltage caps with the same uF.
Since ESR and Ripple are based on the can size [not uF] all you -usually- have to do is switch to a higher voltage cap to get a bigger can, lower ESR and better Ripple.
[That is if the cap is not so big it won't fit.]

Technically you could go from 6.3v up to a 16v cap but I don't know anyone that likes to do that.
I personally don't do that because if I end up working on it again later I'll think the cap is on 12v when it isn't.
[I'd be looking for 16v caps when a 6.3v or 10v would do.]
-
There is also that some of those 'made on mobo' voltages are as low as 1.5v [and less sometimes].
No one says it's bad to use a cap at less than 10% of it's rated value but it doesn't seem like a good idea to me.
Two reasons.
- In 'the old days' they said not to use them at less than 20-30% [depending on who you asked] of rated voltage.
- There needs to be enough bias on the ions in solution [the electrolyte] to get the chemicals to do what they are supposed to and maintain the oxide layer's thickness. The oxide layer naturally dissolves into solution over time [this is why ltyic caps have a shelf life] and the bias voltage puts the oxide layer back. A tiny voltage in a physically large cap may be 'putting back' the layer slower than the dissolving effect is removing it, and that may eventually send Leakage through the roof. [Which is another way of saying shorted cap.]
.
They say modern caps don't have that problem but, frankly, knowing a little bit about chemistry, I don't believe them.
.

[kleung]

Re: KZJ Series? (Dell Server Motherboard)

Out of curiosity, was this motherboard from a poweredge 840 server.

I have a 840 server where the same caps seem to be failing and i will be performing a repair soon.

luckily, i have a backup server so i will be swapping that motherboard over in the interrim but since that hasn't been recapped and I don't know how many hours, it was used, I am somewhat leary of it.

[bw1]

Re: KZJ Series? (Dell Server Motherboard)

Out of curiosity, was this motherboard from a poweredge 840 server.

Yes, it was. We never ended up doing anything with it. It wasn't currently affecting anything, and was replaced less than a year later for other reasons.

If the info would have been easily accessible I probably would have done it preventatively, but I never found the info I needed, and the server was working properly until it was retired.

[japlytic]

Re: KZJ Series? (Dell Server Motherboard)

I've seen KZJ's bulge on the shelf without any voltage applied.

[kleung]

Re: KZJ Series? (Dell Server Motherboard)

So.... I will add to the knowledge base. I have a 2007 Dell Poweredge 840 Server with the KZJ capacitors.

There is one that shows obvious signs of failure with leaking electrolytes. The ones that failed is a KZJ 6.3 V 1800 uF just like the OP's.

On there board, there are 3 of these KZJ 6.3v 1800 uF capacitors which I have circled on one of the pictures.


Interestingly, I pulled the motherboard out and tested it with an ESR meter and they all showed low/perfect ESR.

I have not changed the caps yet (don't know if I will as I am using my backup server). Also, although there were visible signs of failure; like the OP; the system SEEMS to be functioning fine.

I am not sure if there is redundancy on the motherboard design or it just hasn't manifested itself in a way that I recognize yet.


IF I ever get spare time; I will try and swap out these capacitors as I'm not sure when the backup server's KZG caps will fail (yes, it's the same poweredge 840 but dell used KZG caps and KZJ caps at these locations).


Honestly, with an 7-8 year old server, I really should just virtualize it and move on but I haven't had the time to do so and we still have some important data on it.

Thanks for the quick replies guys and any comments would be appreciated.

Any idea why the ESR value is still low / good even though the capacitor has failed?

[momaka]

Re: KZJ Series? (Dell Server Motherboard)

IF I ever get spare time; I will try and swap out these capacitors as I'm not sure when the backup server's KZG caps will fail (yes, it's the same poweredge 840 but dell used KZG caps and KZJ caps at these locations).

Both KZG and KZJ are prone to the same failures, so both should be replaced. In my experience, KZJ tend to last just a tad-bit longer, but I still wouldn't advise anyone to trust them. If they are in an important piece of equipment, just replace them. If not, roll the dice and see how long they last.

Any idea why the ESR value is still low / good even though the capacitor has failed?

Are you measuring the caps in circuit?
If yes, then it is normal to see a very low ESR, because there are probably more capacitors in parallel with the failed one(s). Basically, your ESR meter is getting fooled. So you can't really test capacitors while they are still attached to the motherboard.

Also, when there is a failed capacitor, the other "good" (or not failed) capacitors in parallel with it will be "working" extra hard to make up for the failed capacitor. This will wear them down faster until they fail too. The more capacitors that fail, the faster they will all fail.

By the way, KZG still tend to appear a lot even in many newer motherboards. So this is not a limited case to just the PowerEdge 840 servers. I think I recall seeing them in other (older) Dell servers too.