8RDA3+ VDD drops when hot - caps?

[denny_crane]

Hi all,

My Epox 8RDA3+ mobo has always been a bit flaky, but these last few weeks it started behaving really badly. Random crashes, complete hangs, BSOD:s...

I suspected the problem was heat-related. Tried cleaning fans+heatsinks and applied new arctic silver, which got the CPU temp down from 50-ish to 40. The problems kept coming. When I opened the case and put a big table fan facing the mobo everything started to work fine.

Then I looked at what was happening in MBM5 and USBM without the table fan providing cooling. Hardly any difference at all in disk, system or cpu temps. The only parameter that changed was that "Core VDD" dropped rapidly from 1.7V to under 1.4V, and somewhere at about 1.3V the mobo crashed consistently (and I don't blame it, it's default voltage is 1.6). So what is causing the VDD voltage to drop to critically low levels when I haven't got a big fan flowing into the case?

Googled the issue and found this site. Could this problem be capacitor related? I see no physical irregularities on the Teaco's. Do motherboards with caps going bad get more temperature sensitive according to your experience?

If bad caps are causing this, is there anything I could do to squeeze another year out of the board? (I guess you'll tell me to change the Teaco caps but I'm not that big on soldering) I'll try to apply cooling to some of the mosfets as a temporary solution. Any other suggestions welcome!

(Hope I didn't bore you to death with my long post but then I suppose the easily bored don't read these forums to begin with!

/ David

[Shroomie]

Re: 8RDA3+ VDD drops when hot - caps?

Teapos are notorious for going bad without any visible signs. I'm guessing you don't have the equipment you need...You have a nice board there, though. You could send it to Topcat and have him recap it, or just buy a new one. My 8RDA3I Pro, a few months old, has all Rubycon and Matsushita/Panasonic (good quality) caps, excepting a few tiny G-Luxons, so you should do OK. EPoX has learned their lesson.

You said Teaco...Sure they aren't Teapo? If they ARE Teaco...oh man, counterfeit badcaps...haha...

[denny_crane]

Re: 8RDA3+ VDD drops when hot - caps?

Teapos are notorious for going bad without any visible signs. I'm guessing you don't have the equipment you need...You have a nice board there, though. You could send it to Topcat and have him recap it, or just buy a new one. My 8RDA3I Pro, a few months old, has all Rubycon and Matsushita/Panasonic (good quality) caps, excepting a few tiny G-Luxons, so you should do OK. EPoX has learned their lesson.

You said Teaco...Sure they aren't Teapo? If they ARE Teaco...oh man, counterfeit badcaps...haha...

Thanks!

And oops, yes, they do say Teapo, even though "Cheapo" comes to mind...

Buying a new board sounds like a way to go, if I can find one to order. I can't be without this rig while sending the board halfway across the world, and also don't want to screw up my XP install by introducing a too different mobo. Any idea how to know which revisions of 8RDAxxx boards that have better caps on them?

Heard anything about the refurbished ones from here: https://www.epoxstore.com/ ?

/ David

[Per Hansson]

Re: 8RDA3+ VDD drops when hot - caps?

Another Swede; hi there and welcome to Badcaps

I've owned a Epox 8RDA3+ rev2.0 for a long time, it also has Teapo caps, it did not fail before I took it out of service, and I ran it highly overclocked all this time 24/7 with poor cooling...

This is in no way to say that you are wrong, just to say that the difference of how poor Teapo caps really are does differ, i.e. they can work for only a few months or several years...

But there is also a design issue with the 8RDA3+ rev 2.0 and below, the row of capacitors right next to the CPU hinders any airflow that otherwise would cool the voltage regulators...

If you take a look at this picture of my board the first 3 capacitors are actually GSC and it is nothing short of amazing they have not failed. These are the 12v input capacitors. Next comes the 6 VRM Mosfets for the 3-phase voltage supply to the CPU. And last is the row of Teapo caps which as you can clearly see hinders airflow... This was fixed in rev 3.x of this board...



So what I want you to do is monitor the temp of these voltage regulators (Mosfets) But please be careful, because they will handle upto 100°C without malfunctioning!
My thinking is that yours are well above 100°C...

And the reason they become so extremley hot is that the capacitors have silently dried out (without visibly bulging which is very common for Teapo caps)
That will make the Mosfets have to work much much harder...

So yes, I think a recap is what your mainboard needs...

https://www.badcaps.net/forum/attach...id=11227&stc=1