2008 MacPro Memory Card Bad Cap

[EasyGoing1]

I have a 2008 MacPro (3,1), and out of nowhere, it shut down. The memory card was smoking from one of the inductors on the card. With the computer turned off, but plugged in, when I insert the memory card (which has 4 DIMMS on it), I hear a clicking noise (just once) and the inductor starts to smoke. Again, this is while the computer is turned off but plugged in.

Upon further investigation, I found a blown cap, and the two next to it were swollen. Also, it looks like maybe an adjacent FET might also be damaged. Here are some photos - you be the judge.

I'm not sure what kinda caps these are, nor am I convinced that simply replacing them will fix my problem.

Any feedback would be much appreciated.

Mike

[petehall347]

Re: 2008 MacPro Memory Card Bad Cap

blue sanyo used to get called capistors ..and still do .. although those ones were from earlier times ..maybe the badness didn't get resolved ..
test those capacitors for short circuit .

[stj]

Re: 2008 MacPro Memory Card Bad Cap

those are OSCON series polymer capacitors.

[EasyGoing1]

Re: 2008 MacPro Memory Card Bad Cap

blue sanyo used to get called capistors ..and still do .. although those ones were from earlier times ..maybe the badness didn't get resolved ..
test those capacitors for short circuit .

Some of them simply couldn't hold their bladder and let loose all over the circuit board .... I dont think testing those would be necessary...

[Drack]

Re: 2008 MacPro Memory Card Bad Cap

Well a bad cap can make the fet (and inductor) extremely hot

[UHU]

Re: 2008 MacPro Memory Card Bad Cap

First step would be to change all the capacitors on the motherboard I would use Panasonic SEPC range for what is shown in your photos - your photo shows makings that should mean 270uF 16Volt.

Panasonic SEPC of today is a newer generation than the Sanyo OS-Cons in your photo - Panasonic IIRC bought the OS-Con division of Sanyo and refined the chemistry involved - have recapped various motherboards (a couple were 10 years old) that had the original mix of electrolytics, Fujitsu polymers and Panasonic SEPC's all on the one board - testing some of the removed polymers showed the SEPC's were still fine while the Fujitsu polymers were shot - it is also notable that the SEPC's cost more so the motherboard manufacturers seem to use them sparingly (to solve problem circuit designs) vs the Fujitsu polymers.

Didn't think your Os-Con's were still on sale for 2008 production runs - maybe Apple had old stock of Os-Con's

Either way I replace ALL the motherboard capacitors and things have always come back to life for me.

Yes the capacitor could make a fet or anything else it is connected to extremely hot because the capacitor could for instance go (effectively) short circuit and become a current draw which will heat up the devices supplying the cap with its excess current.

Once you have done that try it or change the smoking component(s?) and fet's then try it out.

[Mint Waxed]

Re: 2008 MacPro Memory Card Bad Cap

A unit from 2008 has reached the end of it's life so I would replace all electrolytic caps that are accessible.

[EasyGoing1]

Re: 2008 MacPro Memory Card Bad Cap

These caps are on the MEMORY card which is separate from the motherboard ... are you suggesting that I replace every cap in the entire computer or just the ones on the memory card that went bad?

[stj]

Re: 2008 MacPro Memory Card Bad Cap

just do the memory card for now.

the oscon's do go out of spec with age though, i have a load of them i recovered from p3 server boards - half of them were out of spec.

[EasyGoing1]

Re: 2008 MacPro Memory Card Bad Cap

i have a load of them i recovered from p3 server boards - half of them were out of spec.

What do you mean when you say they have gone "out of spec"?

[stj]

Re: 2008 MacPro Memory Card Bad Cap

i mean on the tester the esr had gone up a bit or more common, the uf's had dropped a lot!

none had shorted,leaked or bulged though.

[EasyGoing1]

Re: 2008 MacPro Memory Card Bad Cap

Oh I see ... that makes sense ... so in other words, they were wearing out, and were no longer performing to their stated specifications even though they had not yet completely failed.

[stj]

Re: 2008 MacPro Memory Card Bad Cap

exactly, they would not have done any direct damage.