New caps on motherboard hot

[jayjr1105]

Motherboard is Intel DQ35JO. They have notoriously bad caps below the 24 pin ATX connector (1800uf 6.3v Rubycon MCZ). I successfully replaced both with 2200uf 10v Panasonic FM's. Ran stress tests on the system for several hours and even with the system idle, the caps are measuring 45c on the vent with my k type probe using a multimeter.

I never knew caps to be hot to the touch like this before. Normal?

Yes I know the new caps are 12mm vs 8mm old and it looks bad but there in there good and working.

[dmill89]

Re: New caps on motherboard hot

The FMs have higher ESR than the MCZs you replaced (18 mOhm vs. 12 mOhm) which would cause them to run hotter. I also imagine the original MCZs were running fairly hot to begin with to fail (Rubycon MBZ/MCZ rarely fail unless they are heavily stressed).

[stj]

Re: New caps on motherboard hot

MCZ was the best of the best - and no longer made.
you must use poly's now.

[jayjr1105]

Re: New caps on motherboard hot

The FMs have higher ESR than the MCZs you replaced (18 mOhm vs. 12 mOhm) which would cause them to run hotter. I also imagine the original MCZs were running fairly hot to begin with to fail (Rubycon MBZ/MCZ rarely fail unless they are heavily stressed).

MCZ was the best of the best - and no longer made.
you must use poly's now.

I checked the leads with a meter and it was around 5v. With only a 6.3v cap, I guess that could be why the first ones blew up. Also, I checked the ESR of a new Panasonic 10v 2200uf and it was .03ohm

[dmill89]

Re: New caps on motherboard hot

MCZ was the best of the best - and no longer made.
you must use poly's now.

Unfortunately good motherboard grade electrolytic caps are becoming very hard to come by (since most newer boards are using polymers there isn't much demand anymore).

It looks like DigiKey still has Nichicon HZs in the 1800uf 6.3V size available (9mOhm/.009 ohm impedance) which would be a sutible replacement for MCZs, but that series has been discontinued as well and availability is likely limited to existing stock.

I checked the ESR of a new Panasonic 10v 2200uf and it was .03ohm

Seems a bit on the high side per the specs of those caps .018ohm, but still close enough it could just be meter variance. In any case those FMs are low-ESR caps primarily intended for use in devices like SMPS (switch-mode power-supplies), TVs, etc. while the MCZs are Ultra-Low ESR caps intended for use on motherboards (as are the Nichicon HZs linked above as well as HMs/HNs, etc.).

[jayjr1105]

Re: New caps on motherboard hot

Unfortunately good motherboard grade electrolytic caps are becoming very hard to come by (since most newer boards are using polymers there isn't much demand anymore).

It looks like DigiKey still has Nichicon HZs in the 1800uf 6.3V size available (9mOhm/.009 ohm impedance) which would be a sutible replacement for MCZs, but that series has been discontinued as well and availability is likely limited to existing stock.



Seems a bit on the high side per the specs of those caps .018ohm, but still close enough it could just be meter variance. In any case those FMs are low-ESR caps primarily intended for use in devices like SMPS (switch-mode power-supplies), TVs, etc. while the MCZs are Ultra-Low ESR caps intended for use on motherboards (as are the Nichicon HZs linked above as well as HMs/HNs, etc.).

Could be meter variance. Just tested again and it was .01 (only measures two digits after the decimal). Being they are slightly larger caps and 10v, I think they will be fine. Not like I need this board to last 5 more years.

[Stefan Payne]

Re: New caps on motherboard hot

Just use Kemet A750 caps instead. They are dirt cheap and good replacements for KZG and other wet Ultra Low ESR types because they are rather shitty Polys with rather high ESR...

[CapSwapper]

Re: New caps on motherboard hot

my advice is dump that motherboard. new motherboards don't cost a fortune and they all have polymers

[dmill89]

Re: New caps on motherboard hot

my advice is dump that motherboard. new motherboards don't cost a fortune and they all have polymers

New LGA775 boards are a bit hard to come by these days (granted it isn't too difficult to find used higher-end ones with polymer caps on eBay fairly cheap, but even a "good" 7+ year old used motherboard has some risk, especially LGA sockets that are easily damaged in shipping if no packaged properly), and the few that still exist are aimed at the budget replacement market and don't have all polymer caps (such as this ASRock board with polymers on the VRM, but OST electrolytics everywhere else). A new board (at least one with all polymer caps) would likely mean a new CPU and new RAM as well.

[toldim79]

Re: New caps on motherboard hot

Hy, I would go with it RNL1C182MDS1, it is significantly more expensive but at least has an 8 mOhm ESR. However, i would check the temperature of the MOSFET which is sitting relatively close to the capacitor.

http://ie.farnell.com/nichicon/rnl1c...rad/dp/2807386

[john111]

Re: New caps on motherboard hot

Have you thought about going even higher voltage handling caps