Asrock A770DE+ bad caps

[csh]

Hi,
I have a board from the subject and it is running stable, almost 24/7 for a couple of years now. On recent HDD upgrade i noticed a bulged cap near the NB heatsink, marked with the red rectangle on the picture below (picture taken from Asrock website):


Closeup of the bad cap:


Since that cap is bad, I'd like to replace it to avoid any later unplanned downtime

It is a Samxon GK series 1000uF, 6.3V. The other 24 same model caps look ok.
There are also some of the dreaded United Chemicon KZG series:

Now, a couple of questions:
1. would it be wise to recap also the neighbors of the bad cap? There are 2 more in the row + small Teapo SS series 100uF 16V.
2. What about KZGs, to recap or not to recap?
There are 4 near the VRMs as seen on the picture. No sign of leakage or bulging but they are a little wobbly, possible bulging on the botom?

Thanks, any help is appreciated

[stj]

Re: Asrock A770DE+ bad caps

right now, i would just replace that row of 3 - they are going to get hot from the fets/regulators below them and the heatsink above..

question is what to use - electrolytics or poly's.
what diameter are they - 8mm?

[Per Hansson]

Re: Asrock A770DE+ bad caps

Yea I agree with that^^
But maybe take another close look on those KZG's, as you say they look to be quite far from the PCB, maybe you can look in from the side to see how the bungs look underneath?
Of course with any repair like this you have to weigh cost vs benefit, if system uptime is important to you and you want many more years I'd replace all Samxon and UCC caps on it...

[stj]

Re: Asrock A770DE+ bad caps

keep an eye out for dead or damaged server motherboards - you can rob all the poly's off them

[csh]

Re: Asrock A770DE+ bad caps

OK, I'll replace the 3 Samxon's in a row. They are 8mm.
As for the KZG's, I'll leave them for now. On the first sign of instability they are out.
Changing all the caps on MBO is not economically viable option, it would be cheaper to buy new MBO. It's an old platform anyway so changing MBO would require new CPU, RAM, etc.

I'm not in the server business, the firm I work for has subcontractors for that, could ask guys from hardware dept, they probably have some leftovers but it would be old machines. Polymer caps are usually rated with longer lifespans. Shouldn't we be careful with old caps, i mean they sure have some working hours?
I guess I'll go with electrolytics, this PC would probably be history by the time they fail again
Would have to see what is available online in the EU.
Any recommendations what specific brand/series to look for?

[stj]

Re: Asrock A770DE+ bad caps

i dont think anyone has seen a poly go out of spec because of age yet.
they dont have liquid in them to dry up.

[Stefan Payne]

Re: Asrock A770DE+ bad caps

I'd probably replace those KZGs also, as well as all caps in that circuit. So probably that row of 4.

Depending on availability it can make sense to use polymers instead because you may get them cheaper...
Especially since Ultra Low Impedance Aluminium caps are pretty rare these days...

Here in Germany you really have to look for something equal to NCCs KZG series...
And Polymers are much harder to find, if you don't want a through hole version...

According to the datasheet, the Pana FM are pretty close to the KZGs...

[Per Hansson]

Re: Asrock A770DE+ bad caps

These should work well as replacements for the GK & KZG's I think:

https://www.badcaps.net/store/produc...roducts_id=131

https://www.badcaps.net/store/produc...roducts_id=139

[csh]

Re: Asrock A770DE+ bad caps

Thanks, these look like a good match.

[csh]

Re: Asrock A770DE+ bad caps

Update:
Had a couple of longer power outages, UPS did shut down the PC as expected but it wouldn't come back up so easily
The fans and HDDs would spin but no video output. Shutting it off via the power button and powering back on did the trick - after 2-3 times it would post.
Had some Panasonic FRs 8x20 (1000uF,16V) at hand so used them. A bit higher (20mm vs 12) but the MBO is stable now, no problems.
Of those three replaced Samxon GKs, the bulged one is dead, other two measure 930 and 880 uF, ESR 0.18 and 0.23 respectively. Don't know how precise my chinese T4 is but the new cap measures 995uF/0.05 so i guess it is close enough.
I would probably have noticed that power-on problem before, but once up the PC ran 100% stable, checked with prime a couple of times.
Pic of the new caps attached.