How would you test after recapping a VRM?

[keldeo]

Hi badcaps! Recently aquired an optiplex gx270 for $10. It was bad, it wouldn't even power on , it just flashed an amber LED and immediatly powered off. So I cracked it open and found 10 bad caps, 9 on the VRM one for the northbridge. All were Ruby MCZs. Now, I wasn't certain the caps were going to fix the issue and didn't wanna spend money on new caps, only for that to not work (again). So, I salvged some little yellow Fujitsu caps from another 478 board and I salvaged some KZGs from a newer HP board. (I know KZG, but they were free) So I now have 3 Fujitsu, and 6 KZGs, I ran Y-cruncher for about an hour and everything seemed stable. However, the caps did feel kinda hot to the touch. Another thing is there was a huge decrease in uf. With the Rubies, it had a total of 16200, now it's only 7680. Although I don't know if 1 hour of Y cruncher was enough stress, but I'm also not aware of any other ways to test with these replacement caps. How would you consider it stable?

Ninja edit: It just occured that the KZGs also have lower ripple!

[momaka]

Re: How would you test after recapping a VRM?

If it passes memtest, it's probably fine.

It's also fairly normal for the caps to run hot on these boards, due to the CPU running hot... though that will depend on what kind of cooler you have on the CPU. If you're running a Prescott, make sure it's a copper base heatsink with plenty and very large fins (i.e. lots of surface area.)

If the caps & VRM feel so hot to the touch that they burn your fingers instantly, then either your CPU cooler might not be good enough or the caps might be getting over-stressed. If running just "hot", then congratulations - you have a normal-running P4 board.

All in all, as long as the polymers were 820 uF in capacity, that VRM should be fine. 560 uF might be a little on the low side. Dell / Foxconn sometimes used 820 uF polymers and 1500 uF MCZ and Nichicon HN caps interchangeably on similar Dimension and Optiplex mobo models. The KZGs are not only lower-rated in ripple (about the same spec as Nichicon HM / Rubycon MBZ), but they also don't like heat so very likely won't last too long.

Anyways... IMO, just put Windows or Linux on that system and try it out. If it doesn't crash with regular use (after memtest), and if you feel like spending the time + money, get better caps (820-1200 uF polymers) for it and finish it once and for all.

[keldeo]

Re: How would you test after recapping a VRM?

Perfect, thanks momaka! I learned I have a normal Pentium 4 and as luck would have it, I found another junk motherboard , this one has 820uf Sanyo polymers on the VRM. I'll probably end up throwing those ones in.

[Uranium-235]

Re: How would you test after recapping a VRM?

GX270's and 280's had heat issues, they're common for bad caps

[keldeo]

Re: How would you test after recapping a VRM?

I believe it, read a lot about that. Hopefully these oscons hold up, especially now I threw a Prescott in there, mainly for SSE3 support.

I've also got a GX260 that had 2 swollen HMs.