IBM motherboard loses production line lottery

[pfrcom]

This board from an IBM ThinkCentre 8184 has solid caps in VRM, and a mixture of Rubycon and Chemicon electrolytics elsewhere
In this case, the Chemicon KZG beside the northbridge heatsink lives up to its reputation for disliking heat and is bulging top and bottom
Other KZGs, mixed with Rubycon, still appear OK
Whereas the same model that I use every day scored all Rubycon in the lottery, and shows no sign of any problem

[pfrcom]

Re: IBM motherboard loses production line lottery

Final pic shows replacement TMQ 1500uf 10v recycled from a scrap board, but tested OK on Dick Smith ESR meter before re-use
Also shows underneath an identical TMQ, plus original KZG, both of which have the complex bung which usually means a good capacitor

[kc8adu]

Re: IBM motherboard loses production line lottery

that spot is hot enough to pop mbz!
have 2 now that have.just a bad design to put the cap next to those red hot mosfets.

[Topcat]

Re: IBM motherboard loses production line lottery

I have several of these boards, all of which, the mosfets are cooked along with the MBZ caps.

[kc8adu]

Re: IBM motherboard loses production line lottery

re the title.
i noticed these things with either kzg,mbz,or a mix.
lottery indeed!

[pfrcom]

Re: IBM motherboard loses production line lottery

I have several of these boards, all of which, the mosfets are cooked along with the MBZ caps.

Maybe I got to it just in time

Other side of the PCB, underneath the mosfets beside that capacitor, it's quite discoloured - sort of browny blue, instead of bright blue

[shovenose]

Re: IBM motherboard loses production line lottery

Should i be worried about the kzg caps on my am2/+ msi microatx mobo (out of hp)...???
Are they guaranteed to fail? Or just higher likelyness.
No bulgers/leakers yet...

[pfrcom]

Re: IBM motherboard loses production line lottery

As KC8ADU said earlier, bad design

CPU cooling is by an external case fan which blows (from left to right in my first picture) across the CPU's passive heatsink first, then across the northbridge heatsink

So by the time airflow reaches that capacitor, it's probably quite warm

Compound that with heat from the mosfets beside it, and it's not a good environment for something heat-sensitive

The fan is thermostatically controlled as well, only speeds up when CPU is working hard, so probably minimal airflow most of the time

The board does have other KZGs - the group of four 2200uf 6.3v electrolytics to the right of the polymers are one Rubycon MBZ and three Chemicon KZG, all of which look OK

[PCBONEZ]

Re: IBM motherboard loses production line lottery

Should i be worried about the kzg

Yes

[weirdlookinguy]

Re: IBM motherboard loses production line lottery

If you plan on keeping these boards for a long time you should experiement with putting a poly cap in that spot.

[Logistics]

Re: IBM motherboard loses production line lottery

I just picked up an 8183, and I want to polymod it, but not until I either replace or strengthen the stock PSU. Is there a good replacement for the awkwardly-shaped Acbel PSU?

Matthew

[RJARRRPCGP]

Re: IBM motherboard loses production line lottery

Unfortunately, Chemicon has some 'splaning to do! The KZGs on my Asus A7N8X-X motherboard, next to the processor, bulged when sitting!

They weren't bulged in 2010! They're 3300 uFs.