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Old 06-08-2018, 03:18 PM   #1
RoboDisko
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Default Component identification on graphics card

Hey. I've got a pair of 980ti graphics cards that I'm trying to get working. I bought the pair of them 'broken,' but one of them was working great. Then one day I noticed it wasn't working as well, but still working ok. Due to unbalanced power draw on the 2 pcie power connectors as well as early power throttling, I figured it was a VRM issue. Took it out to fix it up.

These cards have an 8 phase VRM. On the output there is a pair of components is parallel that look like diodes. On the non functional card, 2 of these components appeared burnt. On the functional card, 1 appeared burnt. I went on Mouser and ordered the only diodes that had "330" in the part number (3A 30V shockey).

Anyways, diodes came today. It was immediately apparent that they were the wrong package, and shortly after I was brilliant enough to realize that I was looking at capacitors. The reference designator wasn't a big enough giveaway the first time I suppose. Ugh.

Anways, 330, are we really looking at 33pF caps? That seems really small for... a 250W VRM. And can anyone point me in the correct direction of replacements? Or maybe I'm still missing something?
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Old 06-08-2018, 03:40 PM   #2
RoboDisko
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Default Re: Component identification on graphics card

And just before someone suggests removing and testing a component, I would like to add that I have attempted pulling 2 of the caps already. They use some crazy high-temp solder, and my "good" soldering iron isn't hot enough to melt it. (It's a metcal fixed temp.) My cheap-O adjustable soldering iron does get hot enough to melt it (It'd get hot enough to melt itself if you let it,) but by the time the component comes off, there is typically not enough of it left for an accurate test. If it comes to it, I'll pull one off and test, but hoping someone here can chime in before that.
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Old 06-08-2018, 04:30 PM   #3
petehall347
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Default Re: Component identification on graphics card

they are capacitors ..the c designation gives it away . you could initially test them for being shorted .
when removing try adding fresh solder or flux
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Old 06-08-2018, 05:34 PM   #4
RoboDisko
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Default Re: Component identification on graphics card

Ultimately, all of the capacitors are connected in parallel, as well as all the downstream logic. Line reads about 3 ohms on one and 4 ohms on the other. The non-working one that I'd expect to be shorted is the 4 ohm one.

I was adding leaded solder to the joint, but the quality iron wouldn't melt the joint to spread the lead, and by the time you melt the joint with the higher temp iron completely, I found it more effective to pull it off instead of trying to mix up a reasonable solder blend. This certainly isn't my first time soldering, but might be my first time surface mount lead free soldering.
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Old 06-08-2018, 06:26 PM   #5
PeteS in CA
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Default Re: Component identification on graphics card

I'm guessing 330uF tantalum caps.
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Old 06-08-2018, 09:20 PM   #6
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Default Re: Component identification on graphics card

I'm guessing you're 100% right! I can find product offerings that meet those specs with the same physical package size as the ones I desoldered. Man, those suckers can be pricey! Mouser lists 330uF tantalum 7343 caps up to $30 each! Lucky, the ones I want are also the cheapest at $.73 each! (lowest ESR, one voltage range higher than I think I need) I'll get some ordered and let ya know how it goes.

By the way, anyone have a use for 16 b330a diodes?
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